#include <bits/stdc++.h>
using namespace std;
long n;
string s, x;
long a[9];
int main() {
  cin >> n >> s;
  while (s[0] == '0') {
    s.replace(0, 1, "");
    n--;
  }
  for (int i = 0; i < n; i++) {
    int m;
    m = s[i] - 48;
    for (int j = 2; j <= m; j++) {
      if (j == 2) a[2]++;
      if (j == 3) {
        a[3]++;
        a[2]--;
      }
      if (j == 4) a[2] += 2;
      if (j == 5) {
        a[5]++;
        a[3]--;
        a[2] -= 2;
      }
      if (j == 6) a[3]++;
      if (j == 7) {
        a[7]++;
        a[3]--;
        a[5]--;
      }
      if (j == 8) a[2] += 3;
      if (j == 9) {
        a[3] += 2;
        a[2] -= 2;
      }
    }
  }
  x = "";
  for (int i = 7; i > 1; i--)
    if (a[i] > 0)
      for (int j = 1; j <= a[i]; j++) x += i + '0';
  cout << x;
}
