A. Olesya and Rodion
time limit per test

1 second

memory limit per test

256 megabytes

input

standard input

output

standard output

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

题意; 输出一个数  长度为n并且为t的倍数  不存在 则输出-1

题解: n个t  组成的数一定是t的倍数  
考虑特殊 t=10的情况 (水)
 #include<iostream>
#include<cstring>
#include<cstdio>
#include<queue>
#include<stack>
#include<cmath>
#define ll __int64
#define pi acos(-1.0)
#define mod 1000000007
using namespace std;
int n,t;
int main()
{
scanf("%d %d",&n,&t);
if(t<)
{
for(int i=;i<=n;i++)
printf("%d",t);
cout<<endl;
}
if(t==)
{
if(n==)
cout<<"-1"<<endl;
else
{
for(int i=;i<n;i++)
printf("",t);
cout<<""<<endl;
}
}
return ;
}

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