#include <bits/stdc++.h>
using namespace std;
int Facteurs[4];
int Liste[4] = {2, 3, 5, 7};
void DetermineFacteur(string s) {
  for (int j = 0; j < 4; j++) Facteurs[j] = 0;
  for (int i = 0; i < (int)s.length(); i++) {
    int cur = s[i] - '0';
    int facto = 1;
    for (int l = 2; l <= cur; l++) facto *= l;
    for (int j = 0; j < 4; j++) {
      while (facto % Liste[j] == 0) {
        facto /= Liste[j];
        Facteurs[j]++;
      }
    }
  }
}
int CombienRetirer[4][4];
void Solve() {
  for (int i = 0; i < 4; i++)
    for (int j = 0; j < 4; j++) {
      if (j <= i)
        CombienRetirer[i][j] = 1;
      else
        CombienRetirer[i][j] = 0;
    }
  CombienRetirer[2][0] = 3;
  CombienRetirer[3][0] = 4;
  CombienRetirer[3][1] = 2;
  for (int i = 3; i >= 0; i--) {
    for (int l = 0; l < Facteurs[i]; l++) cout << Liste[i];
    for (int j = 0; j < 4; j++) {
      Facteurs[j] -= (CombienRetirer[i][j] * Facteurs[i]);
    }
  }
}
int main() {
  int n;
  cin >> n;
  string s;
  cin >> s;
  DetermineFacteur(s);
  Solve();
}
