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 java.io.BufferedReader;
import java.io.InputStreamReader;

public class A317 {
    public static void main(String[] args) throws Exception {
        BufferedReader ip = new BufferedReader(new InputStreamReader(System.in));
        String s = ip.readLine();
        String[] sp = s.split(" ");
        long a = Long.parseLong(sp[0]);
        long b = Long.parseLong(sp[1]);
        long c = Long.parseLong(sp[2]);
        long ans = 0, tmp;
        

        if(b < a)
        {
            ans = a;
            a = b;
            b = ans;
        }
        
        if(c <= 0)
        {
            if(b >= c)
            {
                System.out.print("0");
                return;
            } else
            {
                System.out.println("-1");
                return;
            }
        } else
        {
            if(b <= 0)
            {
                System.out.print("-1");
                return;
            }
        }

/*      
        if(c < 0)
        {
            c = -1*c;
            a = -1*a;
            b = -1*b;
        }       
*/      
        
        tmp = b;
        
        ans = 0;
        
        if(a < 0 && b > 0 && b < c)
        {
            ans = Math.abs(a / b);
            a = -1*Math.abs(a % b);
        }
        
        for(;;)
        {
            if(tmp >= c)
                break;
            
            if(a <= b)
            {
                ans++;
                
                a = a + b;
                tmp = b;
                if(a > b)
                    tmp = a;
            }
            
            if(tmp >= c)
                break;

            if(b < a)
            {
                ans++;
                
                b = b + a;
                tmp = a;
                if(b > a)
                    tmp = b;
            }
//          System.out.println(a+"\t"+b+"\t"+tmp);
        }
        
        System.out.print(ans);
    }
}