#include <bits/stdc++.h>
using namespace std;
int main()
{
int i, n=25;
char tab[n];
for(i=0;i<n;i++)
{
cin>>tab[i];
}
cout<<tab[3];
sort(tab, tab+n);
cout<<tab[3];
if(tab[0]=='A')
{
cout<<tab[0];
}
return 0;
}
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