#include <bits/stdc++.h>
using namespace std;
const int mod = 1e9 + 7;
int n;
long long a;
int s[10];
void deal(int a) {
  for (int i = a; i >= 2; i--) {
    s[i]++;
  }
  return;
}
void print(int a) {
  if (a == 2) {
    s[2]--;
    cout << 2;
  }
  if (a == 3) {
    s[3]--;
    s[2]--;
    cout << 3;
  }
  if (a == 4) {
    s[2] -= 3;
    s[3]--;
    cout << 4;
  }
  if (a == 5) {
    s[2] -= 3;
    s[3]--;
    s[5]--;
    cout << 5;
  }
  if (a == 6) {
    s[2] -= 4;
    s[3] -= 2;
    s[5]--;
    cout << 6;
  }
  if (a == 7) {
    s[2] -= 4;
    s[3] -= 2;
    s[5]--;
    s[7]--;
    cout << 7;
  }
}
int main() {
  scanf("%d", &n);
  scanf("%lld", &a);
  while (a) {
    deal(a % 10);
    a /= 10;
  }
  s[3] += s[9] * 2;
  s[2] += s[8] * 3;
  s[3] += s[6];
  s[2] += s[6];
  s[2] += s[4] * 2;
  n = s[7];
  for (int i = 1; i <= n; i++) {
    print(7);
  }
  n = s[5];
  for (int i = 1; i <= n; i++) {
    print(5);
  }
  n = s[3];
  for (int i = 1; i <= n; i++) {
    print(3);
  }
  n = s[2];
  for (int i = 1; i <= n; i++) {
    print(2);
  }
  cout << endl;
  return 0;
}
