#include <bits/stdc++.h>
using namespace std;
int factorPow(int& n, int d) {
  int cnt = 0;
  while (n > 0 && n % d == 0) {
    n /= d;
    cnt++;
  }
  return cnt;
}
void solve() {
  int n;
  cin >> n;
  string a;
  cin >> a;
  vector<int> digits(n);
  for (int i = 0; i < n; i++) {
    digits[i] = a[i] - '0';
  }
  vector<int> fact(10);
  fact[0] = 1;
  for (int i = 1; i <= 9; i++) {
    fact[i] = i * fact[i - 1];
  }
  vector<int> primes{2, 3, 5, 7};
  string ans = "";
  for (int i = 0; i < n; i++) {
    int f = fact[digits[i]];
    for (int j = 3; j >= 0; j--) {
      ans.append(factorPow(f, fact[primes[j]]), primes[j] + '0');
    }
  }
  sort(ans.begin(), ans.end());
  reverse(ans.begin(), ans.end());
  cout << ans;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(NULL);
  solve();
  return EXIT_SUCCESS;
}
