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.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.*;

public class Main {

    public static void main( String[] args ) {
        InputReader scan = new InputReader( System.in );
        int n = scan.nextInt();
        int t = scan.nextInt();
        if ( t == 10 ) {
            if ( n == 1 ) {
                System.out.print( -1 );
            } else {
                --n;
                for ( int i = 0; i < n; ++i ) {
                    System.out.print( 1 );
                }
                System.out.print( 0 );
            }
            System.exit( 0 );
        }
        for ( int i = 0; i < n; ++i ) {
            System.out.print( t );
        }
    }

    private static class InputReader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;

        public InputReader( InputStream stream ) {
            reader = new BufferedReader( new InputStreamReader( stream ), 32768 );
            tokenizer = null;
        }

        public String next() {
            while ( tokenizer == null || !tokenizer.hasMoreTokens() ) {
                try {
                    tokenizer = new StringTokenizer( reader.readLine() );
                } catch ( IOException e ) {
                    throw new RuntimeException( e );
                }
            }
            return tokenizer.nextToken();
        }

        public int nextInt() {
            return Integer.parseInt( next() );
        }

        public long nextLong() {
            return Long.parseLong( next() );
        }
    }
}