#include <bits/stdc++.h>
using namespace std;
int a[10];
int main() {
  int n;
  char c;
  scanf("%d", &n);
  memset(a, 0, sizeof(a));
  for (int i = 1; i <= n; i++) {
    scanf(" %c", &c);
    int t = c - '0';
    if (t == 1) a[1]++;
    if (t == 2) a[2]++;
    if (t == 3) a[3]++;
    if (t == 4) a[2] += 2, a[3]++;
    if (t == 5) a[5]++;
    if (t == 6) a[5]++, a[3]++;
    if (t == 7) a[7]++;
    if (t == 8) a[7]++, a[2] += 3;
    if (t == 9) a[7]++, a[3] += 2, a[2]++;
  }
  bool b = 0;
  for (int i = 9; i > 1; i--) {
    if (a[i] != 0 || b == 1) {
      b = 1;
      for (int j = 0; j < a[i]; j++) printf("%d", i);
    }
  }
  printf("\n");
  return 0;
}
