#include <bits/stdc++.h>
using namespace std;
int n, i, j, num, b[1000000];
int jie(int x) {
  int res = 1;
  for (int i = 1; i <= x; i++) res *= i;
  return res;
}
bool cmp(int a, int b) { return a > b; }
int main() {
  scanf("%d\n", &n);
  for (i = 1; i <= n; i++) {
    int x = getchar() - '0';
    if (x <= 1) continue;
    if (x <= 3)
      b[++num] = x;
    else if (x == 4)
      b[++num] = 2, b[++num] = 2, b[++num] = 3;
    else if (x == 5)
      b[++num] = x;
    else if (x == 6)
      b[++num] = 5, b[++num] = 3;
    else if (x == 7)
      b[++num] = x;
    else if (x == 8) {
      b[++num] = 7;
      for (j = 1; j <= 3; j++) b[++num] = 2;
    } else {
      b[++num] = 7;
      b[++num] = 3, b[++num] = 3;
      b[++num] = 2;
    }
  }
  sort(b + 1, b + num + 1, cmp);
  for (i = 1; i <= num; i++) printf("%d", b[i]);
  return 0;
}
