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.
import sys
x, y, m = map(int, sys.stdin.readline().split(" "))

def dist(d, x):
    if d % x == 0:
        return d / x
    else:
        return d / x + 1

def heuristic(x, y, m):
    s = x + y

    if min(dist(m - s, x), dist(m - x, s)) < min(dist(m - s, y), dist(m - y, s)):
        return True
    return False

if x >= m or y >= m:
    print 0
elif x <= 0 and y <= 0:
    print -1
else:
    moves = 0
    while x < m and y < m:
        if x <= 0:
            diff = ((-x) / y) + 1
            x = x + diff * y
            moves = moves + diff
        elif y <= 0:
            diff = ((-y) / x) + 1
            y = y + diff * x
            moves = moves + diff
        elif x + y >= m:
            y = x + y
            moves = moves + 1
        else:
            newx = max(x + 2 * y, 2 * x + y)
            y = x + y
            x = newx
            moves = moves + 2
    print moves
