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.*;
import java.math.BigInteger;
public class OlesyaRodion {

    public static void main(String[] args) {
        Scanner stdIn = new Scanner(System.in);
        int n = Integer.parseInt(stdIn.next());
        int k = Integer.parseInt(stdIn.next());
        
        BigInteger b1 = new BigInteger("1");
        for(int i=1;i<n;i++){
            b1 = b1.multiply(new BigInteger("10"));
        }
        BigInteger b2;
        b2 = b1.multiply(new BigInteger("10"));
        b1 = b1.divide(new BigInteger(k+""));
        b1 = b1.add(new BigInteger("1"));
        b1 = b1.multiply(new BigInteger(k+""));
        BigInteger b3 = new BigInteger("0");
        boolean flag = true;
        while(b1.compareTo(b2)==-1){
            if(b1.mod(new BigInteger("10"))!=b3){
                flag = false;
                System.out.print(b1);
                break;
            }
            b1 = b1.add(new BigInteger(k+""));
        }
        if(flag)
            System.out.print("-1");
    }
    
}