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 ag():
  a,b,m = map(int,input().split())
  x = min(a,b)
  y = max(a,b)
  res = 0
  if x >= m or y >= m:
    return 0
  elif y<=0:
    return "-1"
  if x<0:
    res += (abs(x)+y-1)/y
    x += y*abs(x)//y
  while y < m:
    x1 = y 
    y = y + x
    x = x1
    res += 1
  return res
print(ag())
	  	    			 	    			     		 			