#include <bits/stdc++.h>

using namespace std;

const int MAXN = 4<<17;

int arr[2][MAXN];

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    int n;
    string s;

    cin>>n>>s;

    for (int z = 0; z <= 1; ++z) {
        for (int i = 0, l = 0, r = 0; i < n; ++i) {
            int t = r - i + !z;
            if (i < r) arr[z][i] = min(t, arr[z][l + t]);
            int L = i - arr[z][i], R = i + arr[z][i]-!z;
            while (L >= 1 && R + 1 < n && s[L - 1] == s[R + 1])
                arr[z][i]++, L--, R++;
            if (R > r) l = L, r = R;
        }
    }

    int sol = 0;
    for (int i = 0; i < n; ++i) {
        if (i + arr[1][i] + 1 == n)
            sol = max(sol, 2 * arr[1][i] + 1);
    }
    for (int i = 0; i < n; ++i) {
        if (i + arr[0][i] == n)
            sol = max(sol, 2 * arr[0][i]);
    }

    cout<<n - sol<<'\n';
    return 0;
}