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.*;
import java.util.*;
import java.math.BigInteger;
import static java.lang.Math.*;
import static java.math.BigInteger.*;

public class Main {

    BufferedReader br;
    StringTokenizer in;
    PrintWriter out;

    String next() throws IOException {
        while( in==null || !in.hasMoreTokens() )
            in = new StringTokenizer( br.readLine() );
        return in.nextToken();
    }

    int nextInt() throws IOException {
        return Integer.parseInt(next());
    }

    long nextLong() throws IOException {
        return Long.parseLong(next());
    }

    public static void main(String[] args) throws IOException {
        new Main().run();
    }





    void run() throws IOException {
        boolean oj = System.getProperty("ONLINE_JUDGE") != null;
        Reader reader = oj ? new InputStreamReader(System.in) :
                new FileReader("input.txt");
        br = new BufferedReader(reader);
        out = new PrintWriter(
                oj ? new OutputStreamWriter(System.out) :
                        new FileWriter("output.txt"));
        solve();
        //deb();
        out.flush();
    }

    BigInteger a, b, m;

    void try_swap(){
        if( a.compareTo(b) == 1 ){
            BigInteger c = a;
            a = b;
            b = c;
        }
    }

    void solve() throws IOException {
        a = valueOf(nextLong());
        b = valueOf(nextLong());
        m = valueOf(nextLong());
        try_swap();
        if( b.compareTo(m)>=0 ) out.println(0);
        else{
            if( b.compareTo(ZERO)<= 0 ){
                out.println( -1 );
                return;
            }
            BigInteger cnt = ZERO;
            if( a.compareTo(ZERO)==-1 ){
                cnt = a.negate().divide(b);
                a = a.add( cnt.multiply(b) );
            }
            for( ; b.compareTo(m)==-1 ; cnt = cnt.add(ONE) ){
                BigInteger s = a.add(b);
                a = b;
                b = s;
                try_swap();
//                out.println(a + " " + b);
            }
            out.println(cnt);
        }
    }



}
