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.


read_ints = lambda: map(int, raw_input().split())

def cal(a, b, n):
    ret= 0
    while(1):
        if(a>b):    
            a,b= b,a
        if(b>=n):
            break
        a,b= b,a+b
        ret+= 1

    return ret

a, b, n= read_ints()
ans= 0
if(a>b):
    a,b= b,a
  
if (b>n):
    print "0"  
elif b<=0:
    if b<n:
        print "-1"
    else:
        print "0" 
elif b>0 and a<=0:
    ans+= abs(a)/b
    a+= ans*b
    if(a<=0):
        ans+= 1
        a+= b
    ans+= cal(a,b,n)
    print ans
else: 
    ans+= cal(a,b,n)
    print ans
    

        
        