#include <bits/stdc++.h>
using namespace std;
int main() {
  int i, j, k, m, n;
  string s;
  int number[12];
  while (cin >> n) {
    memset(number, 0, sizeof(number));
    cin >> s;
    for (i = 0; i < s.size(); i++) {
      j = s[i] - '0';
      if (j == 2 || j == 3 || j == 5 || j == 7)
        number[j]++;
      else if (j == 4) {
        number[2] = number[2] + 2;
        number[3]++;
      } else if (j == 6) {
        number[3]++;
        number[5]++;
      } else if (j == 8) {
        number[2] = number[2] + 3;
        number[7]++;
      } else if (j == 9) {
        number[3] = number[3] + 2;
        number[2]++;
        number[7]++;
      }
    }
    for (i = 9; i > 1; i--) {
      while (number[i]) {
        cout << i;
        number[i]--;
      }
    }
    cout << endl;
  }
  return 0;
}
