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.
from re import *
from sys import stderr
def readint():
    return int(raw_input())
def readfloat():
    return float(raw_input())
def readarray(N, foo=raw_input):
    return [foo() for i in xrange(N)]
def readlinearray(foo=int):
    return map(foo, raw_input().split())

def NOD(a, b):
    while b:
        a,b = b, a%b
    return a

def gen_primes(max):
    primes = [1]*(max+1)
    for i in range(2, max+1):
        if primes[i]:
            for j in range(i+i, max+1, i):
                primes[j] = 0
    primes[0] = 0
    return [x for x in range(max+1) if primes[x]]

def is_prime(N):
    i = 3
    if not(N % 2):
        return 0
    while i*i < N:
        if not(N % i):
            return 0
        i += 3
    return 1

x, y, m = readlinearray()

def answer(x, y, m):
    #print x, y, m
    x, y = max(x, y), min(x, y)
    if x >= m:
        return 0
    if x <= 0:
        return -1
    if y < 0:
        i = -y / x + 1
        return i + answer(x, y + i*x, m)
    return 1 + answer(x, y + x, m)

print answer(x, y, m)
