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.*;
import java.io.*;
import java.text.*;

public class practice {
    public static void merge(int arr[], int l, int m, int r) {
        int n1 = m - l + 1;
        int n2 = r - m;
        int L[] = new int[n1];
        int R[] = new int[n2];
        for (int i = 0; i < n1; ++i)
            L[i] = arr[l + i];
        for (int j = 0; j < n2; ++j)
            R[j] = arr[m + 1 + j];

        int i = 0, j = 0;

        int k = l;
        while (i < n1 && j < n2) {
            if (L[i] <= R[j]) {
                arr[k] = L[i];
                i++;
            } else {
                arr[k] = R[j];
                j++;
            }
            k++;
        }

        while (i < n1) {
            arr[k] = L[i];
            i++;
            k++;
        }


        while (j < n2) {
            arr[k] = R[j];
            j++;
            k++;
        }
    }

    public static void sort(int arr[], int l, int r) {
        if (l < r) {
            int m = (l + r) / 2;

            sort(arr, l, m);
            sort(arr, m + 1, r);

            merge(arr, l, m, r);
        }
    }

    public static boolean isSubSequence(String str1, String str2, int m, int n) {
        int j = 0;
        for (int i = 0; i < n && j < m; i++)
            if (str1.charAt(j) == str2.charAt(i))
                j++;

        return (j == m);
    }

    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(br.readLine());
        int n = Integer.parseInt(st.nextToken());
        int t = Integer.parseInt(st.nextToken());
        if(t!=10){
            System.out.print(t);
            for(int i=0;i<n-1;i++){
                System.out.print(0);
            }
            System.out.println();
        }
        else{
            if(n == 1){
                System.out.println(-1);
            }
            else{
                System.out.print(1);
                for(int i=0;i<n-1;i++){
                    System.out.print(0);
                }
                System.out.println();
            }
        }
    }
}