#include <bits/stdc++.h>
using namespace std;
bool compare(long long a, long long b) { return a > b; }
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long t = 1;
  while (t-- > 0) {
    long long n;
    cin >> n;
    string str;
    cin >> str;
    vector<long long> arr(10, 0);
    long long temp;
    for (long long i = 0; i < n; i += 1) {
      temp = str[i] - 48;
      if (temp == 9) {
        arr[7] += 1;
        arr[3] += 2;
        arr[2] += 1;
      } else if (temp == 8) {
        arr[7] += 1;
        arr[2] += 3;
      } else if (temp == 7) {
        arr[7] += 1;
      } else if (temp == 6) {
        arr[5] += 1;
        arr[3] += 1;
      } else if (temp == 5) {
        arr[5] += 1;
      } else if (temp == 4) {
        arr[2] += 2;
        arr[3] += 1;
      } else if (temp == 3) {
        arr[3] += 1;
      } else if (temp == 2) {
        arr[2] += 1;
      }
    }
    for (long long i = 7; i >= 2; i -= 1) {
      for (long long j = 0; j < arr[i]; j += 1) {
        cout << i;
      }
    }
  }
  return 0;
}
