3130

#include <iostream>
#include <fstream>
#include <string>
#include <algorithm>

using namespace std;

int dp[1000][1000];

int main() {
    ifstream fin("input.txt");
    ofstream fout("output.txt");

    string str;
    fin >> str;
    for (int i = 0; i < str.size(); i++) dp[i][i] = 1;
    for (int len = 1; len < str.size(); len++)
        for (int beg = 0; beg < str.size(); beg++) {
            if (beg + len < str.size() && str[beg] == str[beg + len])
                dp[beg][beg + len] = max(dp[beg][beg + len], dp[beg + 1][beg + len - 1] + 2);
            dp[beg][beg + len] = max(dp[beg][beg + len], dp[beg + 1][beg + len]);
            dp[beg][beg + len] = max(dp[beg][beg + len], dp[beg][beg + len - 1]);
        }

    fout << dp[0][str.size() - 1] << endl;

    fin.close();
    fout.close();
    return 0;
}