#include <bits/stdc++.h>
using namespace std;
const int INF = (int)2e9;
const long long INFL = (long long)9e18;
const int MAXINT = ((~0) ^ (1 << 31));
const long long MAXLL = ((~0) ^ ((long long)1 << 63));
template <class T>
inline T pow2(T a) {
  return a * a;
}
template <class T>
inline bool mineq(T& a, T b) {
  return (a > b) ? (a = b, true) : false;
}
template <class T>
inline bool maxeq(T& a, T b) {
  return (a < b) ? (a = b, true) : false;
}
int fact[10];
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  int n;
  cin >> n;
  string str;
  cin >> str;
  for (int i = 0; i < (int)(str.size()); i++) {
    if (str[i] == '2') fact[2]++;
    if (str[i] == '3') fact[3]++;
    if (str[i] == '4') {
      fact[2] += 2;
      fact[3]++;
    }
    if (str[i] == '5') fact[5]++;
    if (str[i] == '6') {
      fact[5]++;
      fact[3]++;
    }
    if (str[i] == '7') fact[7]++;
    if (str[i] == '8') {
      fact[7]++;
      fact[2] += 3;
    }
    if (str[i] == '9') {
      fact[7]++;
      fact[2] += 1;
      fact[3] += 2;
    }
  }
  for (int i = 9; i >= (int)(0); i--)
    for (int j = 0; j < (int)(fact[i]); j++) cout << i;
}
