#include <bits/stdc++.h>
using namespace std;
int n;
string num, s = "";
vector<int> myvec;
int main() {
  ios_base::sync_with_stdio(false);
  cin >> n;
  cin >> num;
  for (int i = 0; i < n; i++)
    if (num[i] != '0' && num[i] != '1') myvec.push_back(int(num[i]) - 48);
  for (int i = 0; i < myvec.size(); i++) {
    if (myvec[i] == 2)
      s += "2";
    else if (myvec[i] == 3)
      s += "3";
    else if (myvec[i] == 4)
      s += "322";
    else if (myvec[i] == 5)
      s += "5";
    else if (myvec[i] == 6)
      s += "53";
    else if (myvec[i] == 7)
      s += "7";
    else if (myvec[i] == 8)
      s += "7222";
    else if (myvec[i] == 9)
      s += "7332";
  }
  sort(s.begin(), s.end());
  reverse(s.begin(), s.end());
  cout << s << endl;
}
