#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  string s;
  cin >> n >> s;
  if (s.size() == 1) {
    cout << s << endl;
    return 0;
  }
  cout << '1';
  for (char c : s)
    if (c == '0') cout << '0';
  cout << endl;
  return 0;
}
