#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  string s;
  cin >> s;
  vector<int> a(10, 0);
  for (int i = 0; i < s.length(); ++i) {
    int curr = s[i] - '0';
    if (curr == 2) {
      ++a[2];
    }
    if (curr == 3) {
      ++a[2];
      ++a[3];
    }
    if (curr == 4) {
      a[2] += 3;
      ++a[3];
    }
    if (curr == 5) {
      a[2] += 3;
      ++a[3];
      ++a[5];
    }
    if (curr == 6) {
      a[2] += 4;
      a[3] += 2;
      ++a[5];
    }
    if (curr == 7) {
      a[2] += 4;
      a[3] += 2;
      ++a[5];
      ++a[7];
    }
    if (curr == 8) {
      a[2] += 7;
      a[3] += 2;
      ++a[5];
      ++a[7];
    }
    if (curr == 9) {
      a[2] += 7;
      a[3] += 4;
      ++a[5];
      ++a[7];
    }
  }
  string ans = "";
  for (int i = 0; i < a[7]; ++i) ans += "7";
  a[2] -= 4 * a[7];
  a[3] -= 2 * a[7];
  a[5] -= a[7];
  a[7] = 0;
  for (int i = 0; i < a[5]; ++i) ans += "5";
  a[2] -= 3 * a[5];
  a[3] -= a[5];
  a[5] = 0;
  for (int i = 0; i < a[3]; ++i) ans += "3";
  a[2] -= a[3];
  for (int i = 0; i < a[2]; ++i) ans += "2";
  cout << ans << endl;
}
