#include <bits/stdc++.h>
using namespace std;
int ans[100];
int cou = 0;
char s[20];
int main() {
  int n;
  int t;
  scanf("%d %s", &n, s);
  for (int i = 0; i < n; ++i) {
    t = s[i] - '0';
    if (t <= 1) continue;
    if ((t & 1 && t != 9) || t == 2) ans[cou++] = t;
    if (t == 4) {
      ans[cou++] = 3;
      ans[cou++] = 2;
      ans[cou++] = 2;
    }
    if (t == 6) {
      ans[cou++] = 5;
      ans[cou++] = 3;
    }
    if (t == 8) {
      ans[cou++] = 7;
      ans[cou++] = 2;
      ans[cou++] = 2;
      ans[cou++] = 2;
    }
    if (t == 9) {
      ans[cou++] = 7;
      ans[cou++] = 2;
      ans[cou++] = 3;
      ans[cou++] = 3;
    }
  }
  sort(ans, ans + cou);
  for (int i = cou - 1; i >= 0; --i) cout << ans[i];
  cout << endl;
  return 0;
}
