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:
import java.util.Scanner;
import java.math.BigInteger;

public class Main
{
    private static String makeNumber(int n)
    {
        String s = "1";
        for(int i = 1; i < n; i++) s = s + '0';
        return s;
    }

    public static void main(String[] args)
    {
        Scanner sc = new Scanner(System.in);
        BigInteger x, y, T; int n, t;
        n = sc.nextInt();
        t = sc.nextInt();
        x = new BigInteger(makeNumber(n));
        T = new BigInteger(new Integer(t).toString());
        y = x.mod(T);
        if(!y.equals(BigInteger.ZERO))
        {
            y = x.divide(T);
            y = y.add(BigInteger.ONE);
            x = y.multiply(T);
            int dis = x.compareTo(new BigInteger(makeNumber(n + 1)));
            if(dis == 1 || dis == 0) 
              x = new BigInteger("-1");
        }
        System.out.println(x);
    }
}