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.
def matMul(a, b):
        c = [ [0]*2 for i in xrange(2) ]
        for i in xrange(2):
                for j in xrange(2):
                        for k in xrange(2):
                                c[i][j] += a[i][k] * b[k][j]
        return c

def ok(x, y, n):
        a = [ [0, 1], [1, 1] ]; b = [[1, 0],[0, 1] ]
        while  n:
                if n&1: b = matMul(b, a)
                a = matMul(a, a)
                n >>= 1
        return x*b[0][1] + y*b[1][1]


def deal(x, y, m):
        if y>=m: print 0; return 
        if y<=0 :
                print -1 if y<m else 0; return
        ans = 0
        if x < 0:
                tmp = (abs(x)+y-1)/y
                x = tmp*y+x
                ans = tmp
        if x > y: x, y = y, x
        #print x, y, ans
        l = 0; r = 20000; TT=-1
        while l<=r:
                mid = (l+r)>>1
                tmp = ok(x, y, mid)
                if tmp >= m:
                        TT = mid; r = mid-1
                else : l = mid+1

        print ans + TT

if __name__ == '__main__':
        x, y, m = map(int, raw_input().split() )
        if x > y: x, y = y, x
        deal(x, y, m)
