#include <bits/stdc++.h>
using namespace std;
int n, len = 0;
char num[20], res[100];
bool ok = false;
char cmp(char a, char b) { return a > b; }
int main() {
  cin >> n;
  cin.get();
  cin.get(num, 20, '\n');
  for (int i = 0; i < n; i++) {
    switch (num[i]) {
      case '0':
      case '1':
        ok = true;
        break;
      case '2':
        res[len++] = '2';
        break;
      case '3':
        res[len++] = '3';
        break;
      case '4':
        for (int j = 0; j < 2; j++) res[len++] = '2';
        res[len++] = '3';
        break;
      case '5':
        res[len++] = '5';
        break;
      case '6':
        res[len++] = '3';
        res[len++] = '5';
        break;
      case '7':
        res[len++] = '7';
        break;
      case '8':
        for (int j = 0; j < 3; j++) res[len++] = '2';
        res[len++] = '7';
        break;
      case '9':
        for (int j = 0; j < 2; j++) res[len++] = '3';
        res[len++] = '2';
        res[len++] = '7';
        break;
    }
  }
  res[len] = '\0';
  sort(res, res + len, cmp);
  cout << (len >= n ? res : (ok ? res : num));
  return 0;
}
