#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
#define lli long long int
using namespace std;
 
string ch[10]={"","","2","3","223","5","53","7","7222","7332"};
 
int main()
{
    lli n,t;
	cin >> t;
	while ( t-- )
	{
		cin>>n;
		string str,ans;
		cin>>str;
		for(lli i=0;i<str.length();i++)
			ans+=ch[str[i]-'0'];
		sort(ans.begin(),ans.end());
		reverse(ans.begin(),ans.end());
		cout<<ans<<endl;
	}
    return 0;
}

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

MgoxCjYKMwowMDY=

2
1
6
3
006