#include <bits/stdc++.h>
using namespace std;
#define REP(i, n) for(int(i)=0;(i)<(n);++(i))
#define in(T,V) T V;cin>>V;

int main(){
    in(string,s);
    int n = s.length(), m = n;
    int res = 1;
    auto f = [&s](int i){ return i%2?' ':s[i/2]; };
    n = n * 2 - 1;

    REP(i,n){
        REP(j,n){
            if(i<j||i+j>=n)break;
            if(f(i-j) == f(i+j)){
                int v = i%2 ? (j+1)/2*2 : 1+j/2*2; 
                if(v < m) res = max(res, v);
            } else break;
        }
    }

    cout << res << endl;
}