#include <bits/stdc++.h>
using namespace std;
int f[8];
int main() {
  int n, d, i;
  string a;
  cin >> n;
  cin >> a;
  for (i = 0; i < a.size(); i++) {
    int j = a[i] - '0';
    for (d = j; d > 1; d--) {
      if (d == 7 || d == 5 || d == 3 || d == 2) f[d]++;
      if (d == 9) f[3] += 2;
      if (d == 8) f[2] += 3;
      if (d == 6) {
        f[2]++;
        f[3]++;
      }
      if (d == 4) f[2] += 2;
    }
  }
  for (i = 0; i < f[7]; i++) cout << 7;
  f[5] -= f[7];
  f[3] -= 2 * f[7];
  f[2] -= 4 * f[7];
  for (i = 0; i < f[5]; i++) cout << 5;
  f[3] -= f[5];
  f[2] -= 3 * f[5];
  for (i = 0; i < f[3]; i++) cout << 3;
  for (i = 0; i < f[2] - f[3]; i++) cout << 2;
  cout << endl;
  return 0;
}
