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.io.*;
import java.math.BigInteger;
public class numerodivi{
public static void main(String args[]) throws IOException{
BufferedReader lector = new BufferedReader(new InputStreamReader(System.in));
String tmp[] = lector.readLine().split(" ");
int a = Integer.parseInt(tmp[0]);
int b = Integer.parseInt(tmp[1]);
int r = mulp(10,a-1,b);
while(r<0)r+=b;
if(a==1 && b==10)System.out.println(-1);
else
System.out.println(((new BigInteger("10")).pow(a-1)).add(new BigInteger(""+(b-r))));
}
public static int mulp(int a,int b,int c){
if(b==0)return 1;
if(b==1)return a%c;
if(b%2==1) return (mulp(a,b-1,c)*a)%c;
int t = mulp(a,b/2,c);
return (t*t)%c;
}
}