#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  int n;
  cin >> n;
  char a[n];
  int b[100], k = 0;
  for (int i = 0; i < n; i++) {
    cin >> a[i];
    if (a[i] == '2')
      b[k++] = 2;
    else if (a[i] == '3')
      b[k++] = 3;
    else if (a[i] == '4') {
      b[k++] = 3;
      b[k++] = 2;
      b[k++] = 2;
    } else if (a[i] == '5') {
      b[k++] = 5;
    } else if (a[i] == '6') {
      b[k++] = 5;
      b[k++] = 3;
    } else if (a[i] == '7')
      b[k++] = 7;
    else if (a[i] == '8') {
      b[k++] = 7;
      b[k++] = 2;
      b[k++] = 2;
      b[k++] = 2;
    } else if (a[i] == '9') {
      b[k++] = 7;
      b[k++] = 3;
      b[k++] = 3;
      b[k++] = 2;
    }
  }
  sort(b, b + k, greater<int>());
  for (int i = 0; i < k; i++) cout << b[i];
  cout << endl;
  return 0;
}
