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.
#! /usr/bin/env python

def change(x, y):
    if x > y:
        tmp = y
        y = x
        x = tmp
    return (x, y)

x, y, m = [int(x) for x in input().split()]
if x >= m or y >= m:
    ans = 0
elif x <= 0 and y <= 0:
    ans = -1
else:
    ans = 0
    x, y = change(x, y)
    if x < 0:
        ans = int(-x / y)
        ans += 1
        x = y - (-x % y)
    while y < m:
        tmp = x + y
        x = y
        y = tmp
        x, y = change(x, y)
        ans += 1
print(ans)
