#include <bits/stdc++.h>
using namespace std;
const int SigmaSize = 3;
const int MaxA = 1e5 + 7;
const int MaxB = 2e5 + 7;
const int MaxC = 6e5 + 7;
int n;
char str[233];
int op[MaxA], len;
int main() {
  while (~scanf("%d", &n)) {
    scanf("%s", str);
    len = 0;
    for (int i = 0; i < n; i++) {
      int num = str[i] - '0';
      if (num == 2 || num == 3 || num == 5 || num == 7)
        op[len++] = num;
      else if (num == 4) {
        op[len++] = 2;
        op[len++] = 2;
        op[len++] = 3;
      } else if (num == 6) {
        op[len++] = 3;
        op[len++] = 5;
      } else if (num == 8) {
        op[len++] = 2;
        op[len++] = 2;
        op[len++] = 2;
        op[len++] = 7;
      } else if (num == 9) {
        op[len++] = 2;
        op[len++] = 3;
        op[len++] = 3;
        op[len++] = 7;
      }
    }
    sort(op, op + len);
    for (int i = len - 1; i >= 0; i--) {
      printf("%d", op[i]);
    }
    printf("\n");
  }
  return 0;
}
