#include <bits/stdc++.h>

using namespace std;

int main() {
    int N;
    cin >> N;
    string s;
    cin >> s;
    // we should calculate hash of last N chars
    // also we should calculate hash of last N chars backwards
    uint h0 = 0;
    uint h1 = 0;
    uint h0q = 1;
    const uint Q = 33;
    vector<uint> T0(N);
    vector<uint> T1(N);
    for (int i = N-1; i >= 0; i--) {
        h1 *= Q;
        h1 += s[i];
        T1[i] = h1;

        h0 += s[i] * h0q;
        h0q *= Q;
        T0[i] = h0;

        //cout << T0[i] << " " << T1[i] << endl;
    }
    for (int i = 0; i < N; i++) {
        // hash matching
        if (T0[i] == T1[i]) {

            // real match
            bool good = true;
            for (int k = i; good && k < N; k++) {
                int l = i+N-1-k;
                if (s[k] != s[l]) {
                    good = false;
                }
            }

            if (good) {
                cout << i << endl;
                return 0;
            }

        }
    }
}