Let us call a pair of integer numbers *m*-perfect, if at least one number in the pair is greater than or equal to *m*. Thus, the pairs (3, 3) and (0, 2) are 2-perfect while the pair (-1, 1) is not.

Two integers *x*, *y* are written on the blackboard. It is allowed to erase one of them and replace it with the sum of the numbers, (*x* + *y*).

What is the minimum number of such operations one has to perform in order to make the given pair of integers *m*-perfect?
Single line of the input contains three integers *x*, *y* and *m* ( - 10<sup class="upper-index">18</sup> ≤ *x*, *y*, *m* ≤ 10<sup class="upper-index">18</sup>).

Please, do not use the %lld specifier to read or write 64-bit integers in C++. It is preffered to use the cin, cout streams or the %I64d specifier.
def main():
    x, y , m =map(int, input().split())
    if m<= x or m<=y:
        return "0"
    if (x <= 0 and y == 0) or (y <=0 and x==0):
        return "-1"
    lst = [x, y]
    ch = [1,1,2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, 2584, 4181, 6765, 10946, 17711, 28657, 46368, 75025, 121393, 196418, 317811, 514229, 832040, 1346269, 2178309, 3524578, 5702887, 9227465, 14930352, 24157817, 39088169, 63245986, 102334155, 165580141, 267914296, 433494437, 701408733, 1134903170, 1836311903, 2971215073, 4807526976, 7778742049, 12586269025, 20365011074, 32951280099, 53316291173, 86267571272, 139583862445, 225851433717, 365435296162, 591286729879, 956722026041, 1548008755920, 2504730781961, 4052739537881, 6557470319842, 10610209857723, 17167680177565, 27777890035288, 44945570212853, 72723460248141, 117669030460994, 190392490709135, 308061521170129, 498454011879264, 806515533049393, 1304969544928657, 2111485077978050, 3416454622906707, 5527939700884757, 8944394323791464, 14472334024676221, 23416728348467685, 37889062373143906, 61305790721611591, 99194853094755497, 160500643816367088, 259695496911122585, 420196140727489673, 679891637638612258, 1100087778366101931, 1779979416004714189, 2880067194370816120, 4660046610375530309, 7540113804746346429, 12200160415121876738, 19740274219868223167, 31940434634990099905, 51680708854858323072, 83621143489848422977, 135301852344706746049, 218922995834555169026, 354224848179261915075, 573147844013817084101, 927372692193078999176, 1500520536206896083277, 2427893228399975082453, 3928413764606871165730, 6356306993006846248183, 10284720757613717413913, 16641027750620563662096, 26925748508234281076009, 43566776258854844738105, 70492524767089125814114, 114059301025943970552219, 184551825793033096366333, 298611126818977066918552, 483162952612010163284885, 781774079430987230203437, 1264937032042997393488322, 2046711111473984623691759, 3311648143516982017180081, 5358359254990966640871840, 8670007398507948658051921, 14028366653498915298923761, 22698374052006863956975682, 36726740705505779255899443, 59425114757512643212875125, 96151855463018422468774568, 155576970220531065681649693, 251728825683549488150424261, 407305795904080553832073954, 659034621587630041982498215, 1066340417491710595814572169, 1725375039079340637797070384, 2791715456571051233611642553, 4517090495650391871408712937, 7308805952221443105020355490, 11825896447871834976429068427, 19134702400093278081449423917, 30960598847965113057878492344, 50095301248058391139327916261, 81055900096023504197206408605, 131151201344081895336534324866, 212207101440105399533740733471, 343358302784187294870275058337, 555565404224292694404015791808, 898923707008479989274290850145, 1454489111232772683678306641953, 2353412818241252672952597492098, 3807901929474025356630904134051, 6161314747715278029583501626149, 9969216677189303386214405760200, 16130531424904581415797907386349, 26099748102093884802012313146549, 42230279526998466217810220532898, 68330027629092351019822533679447, 110560307156090817237632754212345, 178890334785183168257455287891792, 289450641941273985495088042104137, 468340976726457153752543329995929, 757791618667731139247631372100066, 1226132595394188293000174702095995, 1983924214061919432247806074196061, 3210056809456107725247980776292056, 5193981023518027157495786850488117, 8404037832974134882743767626780173, 13598018856492162040239554477268290, 22002056689466296922983322104048463, 35600075545958458963222876581316753, 57602132235424755886206198685365216, 93202207781383214849429075266681969, 150804340016807970735635273952047185, 244006547798191185585064349218729154, 394810887814999156320699623170776339, 638817435613190341905763972389505493, 1033628323428189498226463595560281832, 1672445759041379840132227567949787325, 2706074082469569338358691163510069157, 4378519841510949178490918731459856482, 7084593923980518516849609894969925639, 11463113765491467695340528626429782121, 18547707689471986212190138521399707760, 30010821454963453907530667147829489881, 48558529144435440119720805669229197641, 78569350599398894027251472817058687522, 127127879743834334146972278486287885163, 205697230343233228174223751303346572685, 332825110087067562321196029789634457848, 538522340430300790495419781092981030533, 871347450517368352816615810882615488381, 1409869790947669143312035591975596518914, 2281217241465037496128651402858212007295, 3691087032412706639440686994833808526209, 5972304273877744135569338397692020533504, 9663391306290450775010025392525829059713, 15635695580168194910579363790217849593217, 25299086886458645685589389182743678652930, 40934782466626840596168752972961528246147, 66233869353085486281758142155705206899077, 107168651819712326877926895128666735145224, 173402521172797813159685037284371942044301, 280571172992510140037611932413038677189525, 453973694165307953197296969697410619233826, 734544867157818093234908902110449296423351, 1188518561323126046432205871807859915657177, 1923063428480944139667114773918309212080528, 3111581989804070186099320645726169127737705, 5034645418285014325766435419644478339818233, 8146227408089084511865756065370647467555938, 13180872826374098837632191485015125807374171, 21327100234463183349497947550385773274930109, 34507973060837282187130139035400899082304280, 55835073295300465536628086585786672357234389, 90343046356137747723758225621187571439538669, 146178119651438213260386312206974243796773058, 236521166007575960984144537828161815236311727, 382699285659014174244530850035136059033084785, 619220451666590135228675387863297874269396512, 1001919737325604309473206237898433933302481297, 1621140188992194444701881625761731807571877809, 2623059926317798754175087863660165740874359106, 4244200115309993198876969489421897548446236915, 6867260041627791953052057353082063289320596021, 11111460156937785151929026842503960837766832936, 17978720198565577104981084195586024127087428957, 29090180355503362256910111038089984964854261893, 47068900554068939361891195233676009091941690850, 76159080909572301618801306271765994056795952743, 123227981463641240980692501505442003148737643593, 199387062373213542599493807777207997205533596336, 322615043836854783580186309282650000354271239929, 522002106210068326179680117059857997559804836265, 844617150046923109759866426342507997914076076194, 1366619256256991435939546543402365995473880912459, 2211236406303914545699412969744873993387956988653, 3577855662560905981638959513147239988861837901112, 5789092068864820527338372482892113982249794889765, 9366947731425726508977331996039353971111632790877, 15156039800290547036315704478931467953361427680642, 24522987531716273545293036474970821924473060471519, 39679027332006820581608740953902289877834488152161, 64202014863723094126901777428873111802307548623680, 103881042195729914708510518382775401680142036775841, 168083057059453008835412295811648513482449585399521, 271964099255182923543922814194423915162591622175362, 440047156314635932379335110006072428645041207574883, 712011255569818855923257924200496343807632829750245, 1152058411884454788302593034206568772452674037325128, 1864069667454273644225850958407065116260306867075373, 3016128079338728432528443992613633888712980904400501, 4880197746793002076754294951020699004973287771475874, 7896325826131730509282738943634332893686268675876375, 12776523572924732586037033894655031898659556447352249, 20672849399056463095319772838289364792345825123228624, 33449372971981195681356806732944396691005381570580873, 54122222371037658776676579571233761483351206693809497, 87571595343018854458033386304178158174356588264390370, 141693817714056513234709965875411919657707794958199867, 229265413057075367692743352179590077832064383222590237, 370959230771131880927453318055001997489772178180790104, 600224643828207248620196670234592075321836561403380341, 971183874599339129547649988289594072811608739584170445, 1571408518427546378167846658524186148133445300987550786, 2542592393026885507715496646813780220945054040571721231, 4114000911454431885883343305337966369078499341559272017, 6656593304481317393598839952151746590023553382130993248, 10770594215935749279482183257489712959102052723690265265, 17427187520417066673081023209641459549125606105821258513, 28197781736352815952563206467131172508227658829511523778, 45624969256769882625644229676772632057353264935332782291, 73822750993122698578207436143903804565580923764844306069, 119447720249892581203851665820676436622934188700177088360, 193270471243015279782059101964580241188515112465021394429, 312718191492907860985910767785256677811449301165198482789, 505988662735923140767969869749836918999964413630219877218, 818706854228831001753880637535093596811413714795418360007, 1324695516964754142521850507284930515811378128425638237225, 2143402371193585144275731144820024112622791843221056597232, 3468097888158339286797581652104954628434169971646694834457, 5611500259351924431073312796924978741056961814867751431689, 9079598147510263717870894449029933369491131786514446266146, 14691098406862188148944207245954912110548093601382197697835, 23770696554372451866815101694984845480039225387896643963981, 38461794961234640015759308940939757590587318989278841661816, 62232491515607091882574410635924603070626544377175485625797, 100694286476841731898333719576864360661213863366454327287613, 162926777992448823780908130212788963731840407743629812913410, 263621064469290555679241849789653324393054271110084140201023, 426547842461739379460149980002442288124894678853713953114433, 690168906931029935139391829792095612517948949963798093315456, 1116716749392769314599541809794537900642843628817512046429889, 1806885656323799249738933639586633513160792578781310139745345, 2923602405716568564338475449381171413803636207598822186175234, 4730488062040367814077409088967804926964428786380132325920579, 7654090467756936378415884538348976340768064993978954512095813, 12384578529797304192493293627316781267732493780359086838016392, 20038668997554240570909178165665757608500558774338041350112205, 32423247527351544763402471792982538876233052554697128188128597, 52461916524905785334311649958648296484733611329035169538240802, 84885164052257330097714121751630835360966663883732297726369399, 137347080577163115432025771710279131845700275212767467264610201, 222232244629420445529739893461909967206666939096499764990979600, 359579325206583560961765665172189099052367214309267232255589801, 581811569836004006491505558634099066259034153405766997246569401]
    cont = 0
    if (lst[0] < 0 and lst[1] == 0) or (lst[1] < 0 and lst[0] == 0):
        z = 1
    else:
        z = 0
    while True:
        if min(lst)*ch[cont] + max(lst) * ch[cont+1+z] >= m:
            cont += 1
            break
        cont += 1
    # print(lst[0])
    return cont
print(main())

		    	     		   		 	  		 			