318_C. Perfect Pair
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?

Input

Single line of the input contains three integers x, y and m ( - 1018 ≤ x, y, m ≤ 1018).

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.

Output

Print the minimum number of operations or "-1" (without quotes), if it is impossible to transform the given pair to the m-perfect one.

Examples

Input

1 2 5


Output

2


Input

-1 4 15


Output

4


Input

0 -1 5


Output

-1

Note

In the first sample the following sequence of operations is suitable: (1, 2) <image> (3, 2) <image> (5, 2).

In the second sample: (-1, 4) <image> (3, 4) <image> (7, 4) <image> (11, 4) <image> (15, 4).

Finally, in the third sample x, y cannot be made positive, hence there is no proper sequence of operations.
```python
from sys import stdin
from math import ceil

x, y, m = map(int, stdin.readline().split())
ans = 0
if x >= m or y >= m:
    print(ans)
elif x + y > min(x, y):
    ma, mi = max(x, y), min(x, y)
    ans += ((ma - mi) // ma)  # + ((ma - mi) % ma)

    mi, ma = min(ma, mi + ans * ma), max(ma, mi + ans * ma)

    while ma < m:
        ma, mi = ma + mi, ma
        ans += 1

    print(ans)
else:
    print(-1)

```