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