#define _USE_MATH_DEFINES
 
#include <iostream>
#include <iomanip>
#include <sstream>
 
#include <algorithm>
#include <cmath>
 
#include <string>
//#include <array>
#include <list>
#include <queue>
#include <vector>
#include <complex>
#include <set>
#include <map>
 
/////////
#define REP(i, x, n) for(int i = x; i < n; i++)
#define rep(i,n) REP(i,0,n)
#define P(p) cout<<(p)<<endl;
 
#define PII pair<int,int>
/////////
typedef long long LL;
typedef long double LD;
/////////
using namespace::std;
/////////
int ma[52][52];

int main(void){
    std::cin.tie(0); 
    std::ios::sync_with_stdio(false);
    std::cout << std::fixed;//
    //cout << setprecision(16);//
	
	string S;
	cin>> S;
	
	int Len = S.size();

	rep(i,Len){
		rep(j,Len){
			if( S[i] == S[j] ){
				ma[i+1][j+1] = 1 + ma[i][j+2];
			}else{
				ma[i+1][j+1] = 0 + ma[i][j+2];
			}
		}
	}

	int ans = 0;
	int count;
	int k;

	for(int i = 1 ; i <= Len ; ++i ){
		for( int j = i ; j <= Len ; ++j ){
			k = 0;
			count = ma[j][i] - ma[i-1][j+1];
			if( j-i+1 != count )continue;
			if( j-i+1 < Len ){
				ans = max( ans , count );
			}
		}
	}

	P(ans);
	return 0;
}