#include <bits/stdc++.h>
using namespace std;
int n;
char s[100];
int c[100];
int a[100];
int b[100];
int sol() {
  if (scanf("%d", &n) == EOF) return 0;
  scanf("%s", s);
  for (int i = 0; i < 10; i++) c[i] = a[i] = 0;
  for (int i = 0; i < n; i++) {
    int x = s[i] - '0';
    for (int j = 2; j <= x; j++) {
      if (j == 9) a[3] += 2;
      if (j == 8) a[2] += 3;
      if (j == 7) a[7] += 1;
      if (j == 6) {
        a[3] += 1;
        a[2] += 1;
      }
      if (j == 5) a[5] += 1;
      if (j == 4) a[2] += 2;
      if (j == 3) a[3] += 1;
      if (j == 2) a[2] += 1;
    }
  }
  for (; a[7] && a[5] && a[3] >= 2 && a[2] >= 4;) {
    printf("7");
    a[7]--;
    a[5]--;
    a[3] -= 2;
    a[2] -= 4;
  }
  for (; a[5] && a[3] && a[2] >= 3;) {
    printf("5");
    a[5]--;
    a[3]--;
    a[2] -= 3;
  }
  for (; a[3] && a[2];) {
    printf("3");
    a[3]--;
    a[2]--;
  }
  for (; a[2];) {
    printf("2");
    a[2]--;
  }
  puts("");
  return 1;
}
int main() {
  while (sol())
    ;
  return 0;
}
