#include <bits/stdc++.h>
using namespace std;
const int MOD = 1e9 + 7;
const int N = 15;
int cnt[10];
vector<int> ans;
int main() {
  int n;
  cin >> n;
  string s;
  cin >> s;
  for (int i = 0; i < s.size(); i++) {
    if (s[i] == '2') cnt[2]++;
    if (s[i] == '3') {
      cnt[2]++;
      cnt[3]++;
    }
    if (s[i] == '4') {
      cnt[2] += 3;
      cnt[3]++;
    }
    if (s[i] == '5') {
      cnt[2] += 3;
      cnt[3]++;
      cnt[5]++;
    }
    if (s[i] == '6') {
      cnt[2] += 4;
      cnt[3] += 2;
      cnt[5]++;
    }
    if (s[i] == '7') {
      cnt[2] += 4;
      cnt[3] += 2;
      cnt[5]++;
      cnt[7]++;
    }
    if (s[i] == '8') {
      cnt[2] += 7;
      cnt[3] += 2;
      cnt[5]++;
      cnt[7]++;
    }
    if (s[i] == '9') {
      cnt[2] += 7;
      cnt[3] += 4;
      cnt[5]++;
      cnt[7]++;
    }
  }
  if (cnt[7]) {
    cnt[5] = cnt[5] - (cnt[7] * 1);
    cnt[3] = cnt[3] - (cnt[7] * 2);
    cnt[2] = cnt[2] - (cnt[7] * 4);
    for (int i = 0; i < cnt[7]; i++) ans.push_back(7);
  }
  if (cnt[5]) {
    cnt[3] = cnt[3] - (cnt[5] * 1);
    cnt[2] = cnt[2] - (cnt[5] * 3);
    for (int i = 0; i < cnt[5]; i++) ans.push_back(5);
  }
  if (cnt[3]) {
    cnt[2] = cnt[2] - (cnt[3] * 1);
    for (int i = 0; i < cnt[3]; i++) ans.push_back(3);
  }
  if (cnt[2]) {
    for (int i = 0; i < cnt[2]; i++) ans.push_back(2);
  }
  sort(ans.begin(), ans.end());
  reverse(ans.begin(), ans.end());
  for (int i = 0; i < ans.size(); i++) cout << ans[i];
  return 0;
}
