#include <bits/stdc++.h>
using namespace std;
long long int gcd(long long int a, long long int b) {
  if (b == 0) return a;
  a %= b;
  return gcd(b, a);
}
signed main() {
  ios_base::sync_with_stdio(false), cin.tie(NULL), cout.tie(NULL);
  long long int n;
  cin >> n;
  string s;
  cin >> s;
  vector<int> Fa(10, 0);
  for (long long int i = 0; i < n; i++) {
    if (s[i] == '2') Fa[2]++;
    if (s[i] == '3') Fa[3]++;
    if (s[i] == '4') Fa[2] += 2, Fa[3]++;
    if (s[i] == '5') Fa[5]++;
    if (s[i] == '6') Fa[3]++, Fa[5]++;
    if (s[i] == '7') Fa[7]++;
    if (s[i] == '8') Fa[2] += 3, Fa[7]++;
    if (s[i] == '9') Fa[3] += 2, Fa[2]++, Fa[7]++;
  }
  string ans = "";
  for (int i = 9; i >= 2; i--) {
    for (long long int j = 0; j < Fa[i]; j++) {
      ans = ans + (char)('0' + i);
    }
  }
  cout << ans << '\n';
  return 0;
}
