#include <iostream>
#include <string>
#include <algorithm>
using namespace std;
string pallindrom(string s){
string k;
string r;
int i=s.size();
while(i>0){
for(int j=0;j<=(s.size()-i);j++){
k.insert(k.end(),s.begin()+j,s.begin()+j+i);
r=k;
reverse(k.begin(),k.end());
if(k==r)return k;
k.clear();
r.clear();
}
i--;
}
}
int main() {
// your code goes here
string s="";
cout<<pallindrom(s)<<endl;
return 0;
}
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