#include <bits/stdc++.h>
using namespace std;
int cnt[15];
int extra2, extra3;
int n;
string s;
int main() {
  cin >> n >> s;
  for (int i = 0; i < n; i++) {
    if (s[i] == '0' || s[i] == '1') continue;
    if (s[i] == '4') {
      cnt[3]++;
      extra2 += 2;
    } else if (s[i] == '6') {
      cnt[5]++;
      extra3++;
    } else if (s[i] == '8') {
      cnt[7]++;
      extra2 += 3;
    } else if (s[i] == '9') {
      cnt[7]++;
      extra3 += 2;
      extra2 += 1;
    } else {
      cnt[s[i] - '0']++;
    }
  }
  cnt[2] += extra2, cnt[3] += extra3;
  for (int i = 9; i >= 2; i--) {
    while (cnt[i]) {
      cout << i;
      cnt[i]--;
    }
  }
  puts("");
  return 0;
}
