Problem: Olesya loves numbers consisting of n digits, and Rodion only likes numbers that are divisible by t. Find some number that satisfies both of them.

Your task is: given the n and t print an integer strictly larger than zero consisting of n digits that is divisible by t. If such number doesn't exist, print  - 1.

Input

The single line contains two numbers, n and t (1 ≤ n ≤ 100, 2 ≤ t ≤ 10) — the length of the number and the number it should be divisible by.

Output

Print one such positive number without leading zeroes, — the answer to the problem, or  - 1, if such number doesn't exist. If there are multiple possible answers, you are allowed to print any of them.

Examples

Input

3 2


Output

712

Solution (in JAVA):

Solution:
// package mainpackage;

import java.io.*;
import java.util.*;

public class Main {
	public static void main(String[] args) throws Exception {
		new Main().solve();
	}
	
	private BufferedReader reader;
	private StringTokenizer st;
	private int n, t;
	
	private void solve() throws Exception {
		
		reader = new BufferedReader(new InputStreamReader(System.in));
		
		st = new StringTokenizer(reader.readLine());
		
		reader.close();
		
		n = Integer.parseInt(st.nextToken());
		t = Integer.parseInt(st.nextToken());
		
		if (n == 1 && t == 10) {
			System.out.println("-1");
			return;
		}
		
		
		StringBuilder sb = new StringBuilder();
		if (t == 10) {
			for (int i = 0; i < n - 1; ++i) {
				sb.append("1");
			}
			sb.append("0");
		} else {
			for (int i = 0; i < n; ++i) {
				sb.append(t);
			}
		}
		
		System.out.println(sb);
	}
}