using System;
using System.Collections.Generic;
using System.Linq;
using System.IO;
using System.Globalization;
using System.Diagnostics;
using static System.Console;
//using System.Numerics;
//using static System.Math;

class Program
{
    static void Main()
    {
        //SetOut(new StreamWriter(OpenStandardOutput()) { AutoFlush = false });
        new Program().solve();
        Out.Flush();
    }
    Scanner cin = new Scanner();
    readonly int[] dd = { 0, 1, 0, -1, 0 }; //→↓←↑
    readonly int mod = 1000000007;


    void solve()
    {
        var S = cin.next;
        int N = S.Length;
        var A = new int[26];
        var G = Enumerable.Range(0, 26).Select(i => new List<int>()).ToArray();
        for (int i = 0; i < N; i++)
        {
            A[S[i] - 'a']++;
            G[S[i] - 'a'].Add(i);
        }
        //for (int i = 0; i < 26; i++)
        //{
        //    G[i].Add(N + 1);
        //}
        //int ans = 0;
        //for (int i = 0; i < N; i++)
        //{
        //    var c = S[i] - 'a';
        //    int E = G[c].Count;
        //    for (int j = E - 1; j >= 0; j--)
        //    {
        //        int v = G[c][j];
        //        if (j == E - 1) v = N;
        //        if (G[c][j] == i)
        //        {
        //            ans++;
        //            break;
        //        }
        //        int sa = 0;
        //        for (int k = 0; k < 26; k++)
        //        {
        //            int l = upper_bound(G[k], v) - lower_bound(G[k], i);
        //            if (l % 2 == 1) sa++;
        //        }
        //        if (sa >= 2) continue;
        //        ans++;
        //        i = v;
        //        if (sa == 0) i++;
        //        break;
        //    }
        //}
        WriteLine(Math.Max(A.Max(), A.Count(i => i % 2 == 1)));

    }
    int upper_bound(List<int> arr, int val)
    {
        int low = 0, high = arr.Count;
        int mid;

        while (low < high)
        {
            mid = ((high - low) >> 1) + low;
            if (arr[mid] <= val) low = mid + 1;
            else high = mid;
        }
        return low;
    }

    int lower_bound(List<int> arr, int val)
    {
        int low = 0, high = arr.Count;
        int mid;

        while (low < high)
        {
            mid = ((high - low) >> 1) + low;
            if (arr[mid] < val) low = mid + 1;
            else high = mid;
        }
        return low;
    }
}

class Scanner
{
    string[] s; int i;
    char[] cs = new char[] { ' ' };
    public Scanner() { s = new string[0]; i = 0; }
    public string[] scan { get { return ReadLine().Split(); } }
    public int[] scanint { get { return Array.ConvertAll(scan, int.Parse); } }
    public long[] scanlong { get { return Array.ConvertAll(scan, long.Parse); } }
    public double[] scandouble { get { return Array.ConvertAll(scan, double.Parse); } }
    public string next
    {
        get
        {
            if (i < s.Length) return s[i++];
            string st = ReadLine();
            while (st == "") st = ReadLine();
            s = st.Split(cs, StringSplitOptions.RemoveEmptyEntries);
            i = 0;
            return next;
        }
    }
    public int nextint { get { return int.Parse(next); } }
    public long nextlong { get { return long.Parse(next); } }
    public double nextdouble { get { return double.Parse(next); } }
}