#include <bits/stdc++.h>
using namespace std;
struct fast_ios {
  fast_ios() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(20);
  };
} fast_ios_;
template <typename T>
istream &operator>>(istream &is, vector<T> &v) {
  for (auto &x : v) is >> x;
  return is;
}
template <typename T>
ostream &operator<<(ostream &os, vector<T> &v) {
  for (long long i = 0; i < v.size(); i++) {
    cout << v[i];
    if (i != v.size() - 1) cout << endl;
  };
  return os;
}
template <typename T1, typename T2>
ostream &operator<<(ostream &os, pair<T1, T2> p) {
  cout << '(' << p.first << ',' << p.second << ')';
  return os;
}
template <typename T>
void Out(T x) {
  cout << x << endl;
}
template <typename T1, typename T2>
void chOut(bool f, T1 y, T2 n) {
  if (f)
    Out(y);
  else
    Out(n);
}
using vec = vector<long long>;
using mat = vector<vec>;
using Pii = pair<long long, long long>;
using v_bool = vector<bool>;
using v_Pii = vector<Pii>;
const long long mod = 1000000007;
signed main() {
  long long n;
  cin >> n;
  string s;
  cin >> s;
  vec cnt(10, 0);
  for (long long i = (0); i < (n); i++) {
    long long m = s[i] - '0';
    if (m == 2 || m == 3 || m == 5 || m == 7)
      cnt[m]++;
    else if (m == 4) {
      cnt[2] += 2;
      cnt[3] += 1;
    } else if (m == 6) {
      cnt[3] += 1;
      cnt[5] += 1;
    } else if (m == 8) {
      cnt[2] += 3;
      cnt[7] += 1;
    } else if (m == 9) {
      cnt[2] += 1;
      cnt[3] += 2;
      cnt[7] += 1;
    }
  }
  string ans = "";
  for (long long k = (10) - 1; k >= (0); k--)
    for (long long _ = (0); _ < (cnt[k]); _++) ans += '0' + k;
  Out(ans);
  return 0;
}
