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.

import sys
import math
  
x, y, m = [int(x) for x in (sys.stdin.readline()).split()]

res = 0
if(m > 0):
    if(x + y < 0):
        print(-1)
        exit()
        
    while(x < m and y < m):
        if(x <= y):
            x += y
        else:
            y += x
        res += 1
elif(m < 0):
    if(x > 0 and y > 0):
        print(-1)
        exit()
        
    while(x > m and y > m):
        if(x >= y):
            x += y
        else:
            y += x
        res += 1
      
  
        
print(res)

