#include <bits/stdc++.h>

using namespace std;

#define rep(i, a, b) for(int i = a;i < (b);++i)
#define sz(x) (int)(x).size()
typedef vector<int> vi;

void manacher(const string &s) {
    int n = sz(s);
    vi p[2] = {vi(n+1), vi(n)};
    rep(z, 0, 2) for (int i=0,l=0,r=0;i<n;i++) {
        int t = r - i + !z;
        if (i < r) p[z][i] = min(t, p[z][l+t]);
        int L = i - p[z][i], R = i+p[z][i] - !z;
        while (L>=1 && R+1 < n && s[L-1] == s[R+1])
            p[z][i]++, L--, R++;
        if(R>r) l = L, r = R;
    }
    int minimum = s.size();
    for (int i = 0;i < p[0].size();i++) {
        if (i + p[0][i] >= p[0].size() - 1) {
            minimum = min(n - p[0][i] * 2, minimum);
        }
    }

    for (int i = 0;i < p[1].size();i++) {
        if (i + p[1][i] >= p[1].size() - 1) {
            minimum = min(n - p[1][i] * 2 - 1, minimum);
        }
    }
    cout << minimum << endl;
}

int main() {
    ios_base::sync_with_stdio(0);
    int n;
    cin >> n;
    string s;
    cin>> s;
    manacher(s);
    return 0;
}