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())
a, b = max(x, y), min(x, y)
if a >= m:
    print(0)
    exit()
if a <= 0:
    print(-1)
    exit()
res = 0
if b < 0:
    res += -b // a
    b += res * a
if a < b:
    a, b = b, a
while a < m:
    b += a
    res += 1
    if a < b:
        a, b = b, a
print(res)
