#include <fstream>
#include <cstring>
using namespace std;
ifstream fin("palm.in");
ofstream fout("palm.out");
int l,i,j,D[510][510],sol,n;
char s[510],c;
int main(){
    fin>>s;
    n=strlen(s);
    for(c='z';c>='a';c--)
        for(l=2;l<=n;l++)
            for(i=0;i+l-1<=n;i++){
                j=i+l-1;
                if(s[i]==c){
                    D[i][i]=1;
                    if(s[i]==s[j])
                        D[i][j]=max(D[i][j],2+D[i+1][j-1]);
                }
                D[i][j]=max(D[i][j],max(D[i+1][j],D[i][j-1]));
                sol=max(sol,D[i][j]);
            }

    fout<<sol;
    return 0;
}