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.


/*
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 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.StringTokenizer;
import java.util.TreeSet;

/**
 *
 * @author is2ac
 */
public class C_CF {

    public static void main(String[] args) {
        FastScanner57 fs = new FastScanner57();
        PrintWriter pw = new PrintWriter(System.out);
        //int t = fs.ni();
        int t = 1;
        for (int tc = 0; tc < t; tc++) {
            long x = fs.nl(), y = fs.nl(), m = fs.nl();
            long ct = 0L;
            if (y>x) {
                long temp = y;
                y = x;
                x = temp;
                
            }
            //x >= y
            if (x>=m) {
                pw.println(0);
                continue;
            }
            if (x<=0 && y<=0) {
                pw.println(-1);
                continue;
            }
            if (y<0) {
                long ry = -1L * y;
                long d = ry/x;
                if (ry%x!=0) d++;
                y += x * d;
                ct += d;
            }
            while (x<m) {
                y += x;
                if (y>x) {
                long temp = y;
                y = x;
                x = temp;
                }
                ct++;
            }
            //pw.println(res);
            pw.println(ct);
        }
        pw.close();

    }

    public static String print(int[] b) {
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < b.length; i++) {
            sb.append(b[i]);
        }
        return sb.toString();
    }

    public static int recur(int ind, int p, int[] a, Integer[][] dp) {
        if (ind == a.length) {
            return 0;
        }
        int n = (int) (1e9);
        if (dp[ind][p] != null) {
            return dp[ind][p];
        }
        for (int i = 0; i < 3; i++) {
            int c = 1;
            if (i == a[ind]) {
                c--;
            }
            if (i == p) {
                continue;
            }
            n = Math.min(n, recur(ind + 1, i, a, dp) + c);
        }
        return dp[ind][p] = n;
    }

    public static void sort(long[] a) {
        List<Long> list = new ArrayList();
        for (int i = 0; i < a.length; i++) {
            list.add(a[i]);
        }
        Collections.sort(list);
        for (int i = 0; i < a.length; i++) {
            a[i] = list.get(i);
        }
    }

    public static long gcd(long n1, long n2) {
        if (n2 == 0) {
            return n1;
        }
        return gcd(n2, n1 % n2);
    }

}

class UnionFind16 {

    int[] id;

    public UnionFind16(int size) {
        id = new int[size];
        for (int i = 0; i < size; i++) {
            id[i] = i;
        }
    }

    public int find(int p) {
        int root = p;
        while (root != id[root]) {
            root = id[root];
        }
        while (p != root) {
            int next = id[p];
            id[p] = root;
            p = next;
        }
        return root;
    }

    public void union(int p, int q) {
        int a = find(p), b = find(q);
        if (a == b) {
            return;
        }
        id[b] = a;
    }
}

class FastScanner57 {

    BufferedReader br;
    StringTokenizer st;

    public FastScanner57() {
        br = new BufferedReader(new InputStreamReader(System.in), 32768);
        st = null;
    }

    String next() {
        while (st == null || !st.hasMoreElements()) {
            try {
                st = new StringTokenizer(br.readLine());
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return st.nextToken();
    }

    int ni() {
        return Integer.parseInt(next());
    }

    int[] intArray(int N) {
        int[] ret = new int[N];
        for (int i = 0; i < N; i++) {
            ret[i] = ni();
        }
        return ret;
    }

    long nl() {
        return Long.parseLong(next());
    }

    long[] longArray(int N) {
        long[] ret = new long[N];
        for (int i = 0; i < N; i++) {
            ret[i] = nl();
        }
        return ret;
    }

    double nd() {
        return Double.parseDouble(next());
    }

    String nextLine() {
        String str = "";
        try {
            str = br.readLine();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return str;
    }
}
