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.
x,y,m = [int(i) for i in input().split()]
ans = 0

if x < y:
    x, y = y, x

if x >= m:
    print(0)
    exit(0)
    
if x <= 0 and y <= 0:
    print(-1)
    exit(0)

if y <= 0:
    cnt = ( (0 - y) + x - 1) // x
    ans += cnt
    y = cnt * x

for j in range(100):
    if x < y:
        x, y = y, x
    if max(x, y) >= m:
        break
    ans += 1
    y = y + x

print(ans)