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.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {

	public static void main(String [] args ) {
		try{
			String str;			
			BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
			BufferedOutputStream bos = new BufferedOutputStream(System.out);
			String eol = System.getProperty("line.separator");
			byte [] eolb = eol.getBytes();
			byte[] spaceb= " ".getBytes();
			
			
			str  = br.readLine();
			int blank = str.indexOf( " ");
			long x = Long.parseLong(str.substring(0,blank));
			str = str.substring(blank+1);
			blank = str.indexOf( " ");
			long y = Long.parseLong(str.substring(0,blank));
			long m = Long.parseLong(str.substring(blank+1));
			long ans = 0;
			boolean solved = false;
			if((x>=m)||(y>=m)) {
				ans = 0;
				solved  = true;
			} else if ( (x<=0)&&(y<=0)) {
				ans = -1;
				solved  = true;
			} else if(m<=0) {
				if(x>y) {
					m-=y;
					ans += m/x;
					if((m%x)!=0) {
						ans++;
					}
				} else {
					m-=x;
					ans += m/y;
					if((m%y)!=0) {
						ans++;
					}
				}		
				solved  = true;
			} else if(x<=0){
				ans += Math.abs(x)/y;
				if((Math.abs(x)%y)!=0) {
					ans++;
				}
				x += ans * y;
			} else if (y<=0) {
				ans += Math.abs(y)/x;
				if((Math.abs(y)%x)!=0) {
					ans++;
				}
				y += ans * x;
			}
			if(!solved) {
				while((x<m)&&(y<m)) {
					if(x<y) {
						x = x + y ;
					} else {
						y = x + y;
					}
					ans++;
				}
			}
			bos.write(new Long(ans).toString().getBytes());
			bos.write(eolb);
			bos.flush();
		}  catch(IOException ioe) {
			ioe.printStackTrace();
		}
	}
}
