#include <cstdio>
#include <cstring>

#define NMax 505

using namespace std;

char String[NMax];
int N, DP[NMax][NMax], MaxS;

inline int Max (int a, int b)
{
    if (a>b)
    {
        return a;
    }
    return b;
}

void Read ()
{
    freopen ("palm.in", "r", stdin);
    scanf ("%s", String);
    N=strlen (String);
}

void Solve ()
{
    for (int i=N-1; i>=0; --i)
    {
        DP[i][i]=1;
        for (int j=i+1; j<N; ++j)
        {
            if (String[i]!=String[j])
            {
                continue;
            }
            DP[i][j]=2;
            for (int ii=i+1; ii<j; ++ii)
            {
                for (int jj=ii; jj<j; ++jj)
                {
                    if (String[ii]!=String[jj])
                    {
                        continue;
                    }
                    if (String[i]<=String[ii] and String[jj]>=String[j])
                    {
                        DP[i][j]=Max (DP[i][j], DP[ii][jj]+2);
                    }
                }
            }
            MaxS=Max (MaxS, DP[i][j]);
        }
    }
}

void Print ()
{
    freopen ("palm.out", "w", stdout);
    printf ("%d\n", MaxS);
}

int main()
{
    Read ();
    Solve ();
    Print ();
    return 0;
}