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

public class UVA {
    public static void main(String[] args) {
        
        Scanner input = new Scanner(System.in) ;
        
        
        int n = input.nextInt() ;
        long t = input.nextInt() ;
        String st ;
        
        if(n==1)
        {
            if(t==10)
            {
                System.out.println(-1);
                return ;
            }
        }
        
        StringBuffer str = new StringBuffer() ;
      
        for (int i=0 ; i<n ; i++ )
        {
            str.append('9') ;
        }
        
        st = str.toString() ;
        //Integer num = Integer.parseInt(st) ;
        
        BigInteger num = new BigInteger(st) ;
        BigInteger mod ;
        BigInteger i ;
        
        //System.out.println(num);
        
        for ( i = num ; i.compareTo(BigInteger.ZERO)>0 ; i.subtract(BigInteger.ONE) )
        {
            mod = num.mod(BigInteger.valueOf(t)) ;
            if(mod.compareTo(BigInteger.ZERO)==0)
            {
                System.out.println(num);
                return ;
            }
            else
                num = num.subtract(BigInteger.ONE ) ;
        }
        
    }
}