#include <bits/stdc++.h>
using namespace std;
int factor[10][10] = {{0}, {1},    {2}, {3},       {2, 2},
                      {5}, {2, 3}, {7}, {2, 2, 2}, {3, 3}};
int factor_n[10] = {0, 0, 1, 1, 2, 1, 2, 1, 3, 2};
int p_num[10] = {0};
int prime[10] = {1, 1, 1, 1, 0, 1, 0, 1, 0, 0};
int ans[10] = {0};
int main() {
  int a[20];
  int n;
  cin >> n;
  for (int i = 0; i < n; i++) {
    scanf("%1d", &a[i]);
    if (a[i] == 2 || a[i] == 3) {
      ans[a[i]]++;
    } else if (!prime[a[i]]) {
      for (int j = a[i]; j >= 2; j--) {
        if (prime[j]) {
          ans[j]++;
          break;
        }
        for (int k = 0; k < factor_n[j]; k++) {
          p_num[factor[j][k]]++;
        }
      }
    } else
      ans[a[i]]++;
  }
  ans[3] += p_num[3];
  ans[2] += p_num[2] - p_num[3];
  for (int i = 7; i > 1; i--) {
    if (ans[i] != 0) {
      for (int j = 0; j < ans[i]; j++) {
        cout << i;
      }
    }
  }
  return 0;
}
