#include <bits/stdc++.h>
using namespace std;
int main() {
  vector<string> a(9);
  a[0] = "1", a[1] = "2", a[2] = "3", a[3] = "322", a[4] = "5", a[5] = "53",
  a[6] = "7", a[7] = "7222", a[8] = "7332";
  long long int n;
  cin >> n;
  string s;
  cin >> s;
  string p = "";
  for (long long int i = 0; i < n; i++) {
    if (s[i] - '1' == 0) continue;
    p += a[s[i] - '1'];
  }
  sort(p.begin(), p.end());
  reverse(p.begin(), p.end());
  cout << p << "\n";
}
