#include <bits/stdc++.h>
long long int number, digitnumber, digit[20];
int numb[11];
int main() {
  scanf("%lld", &digitnumber);
  scanf("%lld", &number);
  for (int i = 1; i <= digitnumber; i++) {
    numb[number % 10]++;
    number /= 10;
  }
  while (numb[4] != 0) {
    numb[4]--;
    numb[2] += 2;
    numb[3]++;
  }
  while (numb[6] != 0) {
    numb[6]--;
    numb[3]++;
    numb[5]++;
  }
  while (numb[8] != 0) {
    numb[8]--;
    numb[2] += 3;
    numb[7]++;
  }
  while (numb[9] != 0) {
    numb[9]--;
    numb[2]++;
    numb[3] += 2;
    numb[7]++;
  }
  for (int i = 7; i >= 2; i--)
    for (int j = 1; j <= numb[i]; j++) printf("%d", i);
}
