#include <bits/stdc++.h>
using namespace std;
long long dp[20];
int main() {
  memset(dp, 0, sizeof(dp));
  long long n, i, dig;
  cin >> dig;
  cin >> n;
  while (n != 0) {
    long long r = n % 10;
    if (r == 0 || r == 1) {
      n = n / 10;
      continue;
    }
    if (r >= 9) dp[3] += 2;
    if (r >= 8) dp[2] += 3;
    if (r >= 7) dp[7] += 1;
    if (r >= 6) {
      dp[2] += 1;
      dp[3] += 1;
    }
    if (r >= 5) dp[5] += 1;
    if (r >= 4) dp[2] += 2;
    if (r >= 3) dp[3] += 1;
    if (r >= 2) dp[2] += 1;
    n = n / 10;
  }
  vector<long long> v;
  while (dp[7] >= 1 && dp[5] >= 1 && dp[3] >= 2 && dp[2] >= 4) {
    v.push_back(7);
    dp[7] -= 1;
    dp[5] -= 1;
    dp[3] -= 2;
    dp[2] -= 4;
  }
  while (dp[5] >= 1 && dp[3] >= 1 && dp[2] >= 3) {
    v.push_back(5);
    dp[5] -= 1;
    dp[3] -= 1;
    dp[2] -= 3;
  }
  while (dp[3] >= 1 && dp[2] >= 1) {
    v.push_back(3);
    dp[3] -= 1;
    dp[2] -= 1;
  }
  while (dp[2] >= 1) {
    v.push_back(2);
    dp[2] -= 1;
  }
  for (i = 0; i < v.size(); i++) {
    cout << v.at(i);
  }
}
