#include <bits/stdc++.h>
using namespace std;
const long long int mod = 1e9 + 7;
long long int n, m, k, l;
void solve() {
  long long int n;
  cin >> n;
  string s;
  cin >> s;
  string s1 = "";
  for (__typeof(n) i = (0) - ((0) > (n)); i != (n) - ((0) > (n));
       i += 1 - 2 * ((0) > (n))) {
    if (s[i] == '0' or s[i] == '1')
      continue;
    else if (s[i] == '4') {
      s1 += '2';
      s1 += '2';
      s1 += '3';
    } else if (s[i] == '6') {
      s1 += '3';
      s1 += '5';
    } else if (s[i] == '8') {
      s1 += '2';
      s1 += '2';
      s1 += '2';
      s1 += '7';
    } else if (s[i] == '9') {
      s1 += '3';
      s1 += '3';
      s1 += '2';
      s1 += '7';
    } else
      s1 += s[i];
  }
  sort(s1.begin(), s1.end(), greater<char>());
  cout << s1 << "\n";
}
int32_t main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long int t;
  t = 1;
  while (t--) {
    solve();
  }
  return 0;
}
