#include <bits/stdc++.h>
using namespace std;
char ch[20];
int ans[10005];
bool cmp(int x, int y) { return x > y; }
int main() {
  int n, i, num = 0, x;
  cin >> n;
  for (i = 0; i <= n; i++) ch[i] = getchar();
  for (i = 1; i <= n; i++) {
    x = ch[i] - 48;
    if (x == 1 || x == 0) continue;
    if (x == 2)
      ans[++num] = 2;
    else if (x == 3)
      ans[++num] = 3;
    else if (x == 4) {
      ans[++num] = 2;
      ans[++num] = 2;
      ans[++num] = 3;
    } else if (x == 5)
      ans[++num] = 5;
    else if (x == 6) {
      ans[++num] = 3;
      ans[++num] = 5;
    } else if (x == 7)
      ans[++num] = 7;
    else if (x == 8) {
      ans[++num] = 2;
      ans[++num] = 2;
      ans[++num] = 2;
      ans[++num] = 7;
    } else if (x == 9) {
      ans[++num] = 7;
      ans[++num] = 2;
      ans[++num] = 3;
      ans[++num] = 3;
    }
  }
  sort(ans + 1, ans + 1 + num, cmp);
  for (i = 1; i <= num; i++) cout << ans[i];
}
