#include <bits/stdc++.h>
using namespace std;
int pow(int x, int a);
int main() {
  int N, M;
  bool f = false;
  cin >> N >> M;
  int ans = pow(10, N);
  int count = ans - 1;
  int min = pow(10, N - 1);
  vector<int> s(M), c(M);
  for (int i = count; i >= min; i--) {
    for (int j = 0; j < M; j++) {
      int div = pow(10, s.at(j) - 1);
      if (count / div != c.at(j)) {
        break;
      }
      if (j == M - 1 && ans >= i) {
        f = true;
        ans = i;
      }
    }
  }
  if (f) {
    cout << ans << endl;
  } else {
    cout << "-1" << endl;
  }
}
int pow(int x, int a) {
  if (a == 0) {
    return 1;
  }
  for (int i = 0; i < (int)(a - 1); i++) {
    x *= x;
  }
  return x;
}
