#include <bits/stdc++.h>
using namespace std;
long long pf[10];
long long n;
long long x;
long long pw(long long base, long long p) {
  if (p == 0) return 1;
  long long hf = pw(base, p / 2);
  if (p % 2)
    return hf * hf * base;
  else
    return hf * hf;
}
int main() {
  cin >> n;
  cin >> x;
  for (int i = 0; i < n; i++) {
    long long dd = (x / pw(10, i)) % 10;
    while (dd > 1) {
      long long d = dd;
      long long j = 2;
      while (d % j == 0) {
        d = d / j;
        pf[j]++;
      }
      j = 3;
      while (d % j == 0) {
        d = d / j;
        pf[j]++;
      }
      j = 5;
      while (d % j == 0) {
        d = d / j;
        pf[j]++;
      }
      j = 7;
      while (d % j == 0) {
        d = d / j;
        pf[j]++;
      }
      dd--;
    }
  }
  string ans = "";
  long long n7 = pf[7];
  long long n5 = pf[5];
  long long n3 = pf[3];
  long long n2 = pf[2];
  pf[5] = pf[5] - pf[7];
  pf[3] = pf[3] - pf[5] - 2 * pf[7];
  pf[2] = pf[2] - 4 * pf[7] - 3 * pf[5] - pf[3];
  for (int i = 0; i < pf[7]; i++) ans += '7';
  for (int i = 0; i < pf[5]; i++) ans += '5';
  for (int i = 0; i < pf[3]; i++) ans += '3';
  for (int i = 0; i < pf[2]; i++) ans += '2';
  cout << ans << endl;
  return 0;
}
