#include<bits/stdc++.h> using namespace std; string a; char calc(char s) { if(s>=97) s-=32; return s; } bool flag(char s) { if((s>='a'&&s<='z')||(s>='A'&&s<='Z')) return true; return false; } int main() { getline(cin,a); int len=a.size(); int l=0,r=0; int maxx=0; for(int i=0;i<len;i++) { if(flag(a[i])) { for(int j=i+1;j<len;j++) { if(calc(a[i])==calc(a[j])) { int idl=i,idr=j; while(idl<=idr) { char ls,rs; ls=calc(a[idl]); rs=calc(a[idr]); if(ls!=rs||!flag(ls)) break; idl++; while(!flag(a[idl])&&idl<=idr) idl++; idr--; while(!flag(a[idr])&&idl<=idr) idr--; } if(idl>idr&&maxx<j-i+1) { maxx=j-i+1; l=i,r=j; } } } } } for(int i=l;i<=r;i++) cout<<a[i]; return 0; }