#include <bits/stdc++.h>
using namespace std;
const int oo = 1 << 30;
const double PI = M_PI;
const double EPS = 1e-15;
int n;
string second, answer;
int main() {
  cin.sync_with_stdio(false);
  cin >> n;
  cin >> second;
  for (int i = 0; i < n; i++) {
    if (second[i] == '2') answer += "2";
    if (second[i] == '3') answer += "3";
    if (second[i] == '4') answer += "322";
    if (second[i] == '5') answer += "5";
    if (second[i] == '6') answer += "53";
    if (second[i] == '7') answer += "7";
    if (second[i] == '8') answer += "7222";
    if (second[i] == '9') answer += "7332";
  }
  sort(answer.begin(), answer.end());
  reverse(answer.begin(), answer.end());
  cout << answer << endl;
  return 0;
}
