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 = map(int, input().split())
if x <= 0 and y <= 0:
    if x >= m or y >= m:
        print(0)
    else:
        print(-1)
else:
    if x >= m or y >= m:
        print(0)
        exit(0)
    init = 0
    if x <= 0:
        init = (-x+y-1)//y
        x += init*y
    elif y <= 0:
        init = (-y+x-1)//x
        y += init*x
    ctr = 0
    while x < m and y < m:
        if x <= y:
            x += y
        else:
            y += x
        ctr += 1
    print(init+ctr)