#include <fstream>
#include <cstring>
using namespace std;

ifstream f("palm.in");
ofstream g("palm.out");

string s;
int i,n,v[501],sol=0,l[501][501],maxi,j;


int main () {
    f >> s;
    n=s.size();
    for (i=1;i<=n;i++) v[i]=int(s[i-1])-int('a')+1;
    for (i=1;i<=n;i++) l[i][i]=1;
    for (j=1;j<=n;j++) {
        for (i=1;i<=n-j;i++) {
            if (v[i]==v[i+j] && (v[i]>=v[i-1]||v[i+j]>=v[i+j-1])) {
                l[i][i+j]=l[i-1][i+j-1]+2;
            }
            else {
                if (v[i]==v[i+j]) l[i][i+j]=l[i-1][i+j-1];
                l[i][i+j]=max(l[i][i+j],max(l[i+1][i+j],l[i][i+j-1]));
            }
            maxi=max(maxi,l[i][i+j]);
        }
    }
    g << maxi << '\n';
    f.close();g.close();
    return 0;
}