#include <bits/stdc++.h>
using namespace std;
const vector<int> FOUR = {3, 2, 2};
const vector<int> SIX = {5, 3};
const vector<int> EIGHT = {7, 2, 2, 2};
const vector<int> NINE = {7, 3, 3, 2};
int n;
vector<int> acc;
int main() {
  ios_base::sync_with_stdio(0);
  cin >> n;
  for (int i = 0; i < n; ++i) {
    char c;
    cin >> c;
    int x = c - '0';
    if (x > 1) {
      if (x == 4)
        acc.insert(acc.end(), FOUR.begin(), FOUR.end());
      else if (x == 6)
        acc.insert(acc.end(), SIX.begin(), SIX.end());
      else if (x == 8)
        acc.insert(acc.end(), EIGHT.begin(), EIGHT.end());
      else if (x == 9)
        acc.insert(acc.end(), NINE.begin(), NINE.end());
      else
        acc.push_back(x);
    }
  }
  sort(acc.begin(), acc.end());
  reverse(acc.begin(), acc.end());
  for (int x : acc) cout << x;
  cout << endl;
  return 0;
}
