#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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