Codeforces 584 A . Olesya and Rodion

#include<bits/stdc++.h>
using namespace std;

typedef long long LL;

int main()
{
    ios_base::sync_with_stdio(false);

    int n , t;

    while(cin >> n >> t)
    {
        if(t==10)
        {

            if(n==1)
            {
                cout << "-1\n";
                continue;
            }

            cout << "1";

            for(int i=2; i<=n; i++) cout << "0";

            cout << "\n";
            continue;
        }

        for(int i=1; i<=n; i++) cout << t;

        cout << "\n";
    }

    return 0;
}