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.math.*;
import java.util.*;

public class SolutionA{

	public static void main(String[] args){
		new SolutionA().run();
	}
	
	void solve(){
		long a = in.nextLong();
		long b = in.nextLong();
		long r = in.nextLong();
		if(Math.max(a, b) >= r){
			out.println(0);
			return;
		}
		if(Math.max(a, b) <= 0){
			out.println("-1");
			return;
		}
		if(a < b){
			long c = a;
			a = b;
			b = c;
		}
		long t = (a - b + a-1)/a;
		long ans = t;
		b += a * t;
		while(Math.max(a, b) < r){
			t = a + b;
			if(a < b) a = t;
			else b = t;
			ans++;
		}
		out.println(ans);
	}
	

	class Pair implements Comparable<Pair>{
		int x, y;
		Pair(int x, int y){
			this.x = x;
			this.y = y;
		}
		@Override
		public int compareTo(Pair o) {
			if(o.x == x) return ((Integer) y).compareTo(o.y); 
			return ((Integer) x).compareTo(o.x);
		}

	}
	FastScanner in;
	PrintWriter out;
	void run(){
		in = new FastScanner(System.in);
		out = new PrintWriter(new OutputStreamWriter(System.out));
		solve();
		out.close();
	}

	void runIO(){
		try{
			in = new FastScanner(new File("expr.in"));
			out = new PrintWriter(new FileWriter(new File("expr.out")));
			solve();
			out.close();
		}catch(Exception ex){
			ex.printStackTrace();
		}
	}
	class FastScanner{
		BufferedReader bf;
		StringTokenizer st;
		public FastScanner(File f){
			try{
				bf = new BufferedReader(new FileReader(f));
			}
			catch(IOException ex){
				ex.printStackTrace();
			}
		}
		public FastScanner(InputStream is){
			bf = new BufferedReader(new InputStreamReader(is));
		}
		String next(){
			while(st == null || !st.hasMoreTokens()){
				try{
					st = new StringTokenizer(bf.readLine());
				}
				catch(IOException ex){
					ex.printStackTrace();
				}
			}
			return st.nextToken();
		}
		int nextInt(){
			return Integer.parseInt(next());
		}
		double nextDouble(){
			return Double.parseDouble(next());
		}
		float nextFloat(){
			return Float.parseFloat(next());
		}
		String nextLine(){
			try{
				return bf.readLine();
			}
			catch(Exception ex){
				ex.printStackTrace();
			}
			return "";
		}
		long nextLong(){
			return Long.parseLong(next());
		}
		BigInteger nextBigInteger(){
			return new BigInteger(next());
		}
		BigDecimal nextBigDecimal(){
			return new BigDecimal(next());
		}
		int[] nextIntArray(int n){
			int a[] = new int[n];
			for(int i = 0; i < n; i++)
				a[i] = Integer.parseInt(next());
			return a;
		}
		long[] nextLongArray(int n){
			long a[] = new long[n];
			for(int i = 0; i < n; i++)
				a[i] = Long.parseLong(next());
			return a;
		}
	}
}