#include <bits/stdc++.h>
int main(void) {
  char a[60], b[100];
  int i = 0, j = 0, n, J, t;
  scanf("%d", &n);
  getchar();
  gets(a);
  memset(b, 0, sizeof(b));
  for (i = 0; i < n; i++) {
    switch (a[i]) {
      case '0':
        break;
      case '1':
        break;
      case '2':
        b[j] = a[i];
        j++;
        break;
      case '3':
        b[j] = a[i];
        j++;
        break;
      case '4':
        b[j] = '3';
        b[j + 1] = '2';
        b[j + 2] = '2';
        j = j + 3;
        break;
      case '5':
        b[j] = a[i];
        j++;
        break;
      case '6':
        b[j] = '5';
        b[j + 1] = '3';
        j = j + 2;
        break;
      case '7':
        b[j] = a[i];
        j++;
        break;
      case '8':
        b[j] = '7';
        b[j + 1] = '2';
        b[j + 2] = '2';
        b[j + 3] = '2';
        j = j + 4;
        break;
      case '9':
        b[j] = '7';
        b[j + 1] = '3';
        b[j + 2] = '3';
        b[j + 3] = '2';
        j = j + 4;
        break;
    }
  }
  J = strlen(b);
  for (j = 0; j < J; j++) {
    for (i = 0; i < J - j; i++) {
      if (b[i] < b[i + 1]) {
        t = b[i];
        b[i] = b[i + 1];
        b[i + 1] = t;
      }
    }
  }
  printf("%s\n", b);
  return 0;
}
