#include <bits/stdc++.h>
char str[20];
int a[10];
int main() {
  int n;
  while (~scanf("%d", &n)) {
    memset(a, 0, sizeof(a));
    scanf("%s", str);
    int len = strlen(str);
    for (int i = 0; i < len; i++) {
      if (str[i] == '2') {
        a[2]++;
      }
      if (str[i] == '3') {
        a[3]++;
      }
      if (str[i] == '4') {
        a[2] += 2;
        a[3]++;
      }
      if (str[i] == '5') {
        a[5]++;
      }
      if (str[i] == '6') {
        a[5]++;
        a[3]++;
      }
      if (str[i] == '7') {
        a[7]++;
      }
      if (str[i] == '8') {
        a[2] += 3;
        a[7]++;
      }
      if (str[i] == '9') {
        a[3] += 2;
        a[2]++;
        a[7]++;
      }
    }
    for (int i = 7; i >= 2; i--) {
      while (a[i]) {
        printf("%d", i);
        a[i]--;
      }
    }
    printf("\n");
  }
  return 0;
}
