#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, a[10][10] = {0}, ans[10] = {0}, i, j, x;
  string s;
  a[2][2] = 1;
  a[3][3] = 1;
  a[5][5] = 1;
  a[7][7] = 1;
  a[4][3] = 1;
  a[4][2] = 2;
  a[6][5] = 1;
  a[6][3] = 1;
  a[8][7] = 1;
  a[8][2] = 3;
  a[9][7] = 1;
  a[9][3] = 2;
  a[9][2] = 1;
  cin >> n >> s;
  for (i = 0; i <= n - 1; i++) {
    if (s[i] != '0' && s[i] != '1') {
      x = s[i] - '0';
      for (j = 2; j <= 9; j++) {
        ans[j] += a[x][j];
      }
    }
  }
  for (i = 9; i >= 2; i--) {
    for (j = ans[i]; j >= 1; j--) {
      cout << i;
    }
  }
  return 0;
}
