#include <iostream>
#include <vector>
#include <string>
#include <map>
#include <set>
#include <algorithm>
using namespace std;

int main() {
    ios_base::sync_with_stdio(false);
    string s;
    cin >> s;
    int res =0 ;
    int n = (int) s.size();
    vector<int> v[26];

    for(int i = 0; i < n; i++) {
        v[s[i] - 'A'].push_back(i);
    }

    for(int i = 0; i < n; i++) {
        int c = s[i] - 'A';

        for(int k = (int) v[c].size() - 1; k >= 0; k--) {
            int p = v[c][k];
            if(p <= i) break;
            int sz = p - i + 1;
                if(sz % 4 == 0) {
                    sz /= 4;
                    int cnt = 1;
                    bool ok = true;
                    for(int j = i; j < i + sz; j++) {
                        if(s[j] == s[i + 2 * sz - cnt] and s[j] == s[j + 2 * sz] and s[j] == s[i + 4 * sz - cnt]) {

                        }
                        else {
                            ok = false;
                            break;
                        }
                        cnt++;
                    }
                    if(ok) {
                        res = max(res, 4 * sz);
                        i = p;
                        break;
                    }
                }
            }

    }
    cout << res << endl;
    return 0;
}