day con doi xung dai nhat

#include<bits/stdc++.h>
using namespace std;
#define ll long long
int main(){
    string s;
    cin >> s ;
    int n = s.size();
    s=" "+ s;
    int res=0 ;
    int f[n+2][n+2];
    memset(f,0,sizeof(f));
    for (int i=1;i<=n;i++) f[i][i]=1;
    for (int i=n;i>=1;i--){
        // for nguoc de lay nhung truong hop be hon truoc
        for (int j=i+1;j<=n;j++){
            if ( j-i==1 ){
                if ( s[i]==s[j]) f[i][j]=1;
            }
            else {
                f[i][j]= f[i+1][j-1] && (s[i]==s[j]);
            }

            if ( f[i][j] == 1 ) res=max(res,j-i+1);

        }
    }

    cout << res;
    return 0;
}