#include <iostream>
#include <map>
#include <algorithm>
int main()
{
	int n;
	std::string str;
	std::string solutie;

	std::cin >> n;
	std::cin >> str;

	std::map<char, std::string> mapare;
	//transformam orice cifra 0 sau 1 in vid
	mapare['0'] = "";
	mapare['1'] = "";
	//transformam nr prime in ele insusi
	mapare['2'] = "2";
	mapare['3'] = "3";
	mapare['5'] = "5";
	mapare['7'] = "7";
	//numere compuse
	mapare['4'] = "223";
	mapare['6'] = "35";
	mapare['8'] = "2227";
	mapare['9'] = "2337";

	for (int i = 0; i < n; i++) {
		solutie += mapare[str[i]];
	}

	std::sort(solutie.rbegin(), solutie.rend());

	std::cout << solutie;
}