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():
    a, b, m = map(int, input().split())
    if a > b:
        a, b = b, a
    if b >= m:
        print(0)
        return
    i = 0
    if a < 1:
        a, b, i = a + b, b, 1
    if b < 1:
        print(-1)
    else:
        while b < m:
            a, b, i = b, a + b, i + 1
    print(i)


if __name__ == '__main__':
    main()
