#include <stdio.h>
#include <cstring>
#include <cctype>
struct Date
{
    int inceput,lungime;
};
Date din[501];
int main()
{

    freopen("palm.in", "r",stdin);
    freopen("palm.out", "w",stdout);

    char s[501];
    scanf("%s",s+1);
    int lung = strlen(s+1);
    for(int i=1; i<=lung; i++)
    {
        int jmax=-1,lmax=-1,cmax=-1;
        for(int j=i; j>=1; j--)
        {
            if(s[din[j].inceput]>s[i])
            {
                for(int k=din[j].inceput; k>=1; k--)
                {
                    if(s[k]==s[i])
                    {
                        if(din[j].lungime>lmax)
                        {
                            lmax=din[j].lungime;
                            jmax=j;
                            cmax=k;
                        }
                    }
                }

            }
        }
        if(jmax!=-1)
        {
            din[i].inceput=cmax;
            din[i].lungime=din[jmax].lungime+2;
        }
        else
        {
            din[i].inceput=i;
            din[i].lungime=1;
            //ar trebui sa pot include si cel de dinainte!
        }

    }
    int lungmax=-1;
    for(int i=1; i<=lung; i++)
        if(din[i].lungime>lungmax)
         lungmax=din[i].lungime;
    printf("%d",lungmax);
    return 0;
}