#include <bits/stdc++.h>
using namespace std;

const int N = 4e5+5;
const long long A = 1e9+7;
const long long B = 1e9+9;

#define ll long long

int n;
string s;

long long p[N];

int main() {
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	p[0] = 1;
	for (int i = 1; i < N; ++i) {
		p[i] = (p[i-1]*A)%B;
	}
	cin >> n >> s;
	string q(s.rbegin(), s.rend());
	long long h = 0;
	set<long long> sh;
	for (int i = 0; i < n; ++i) {
		h = (h + ((ll)(q[i]-'a'+1)*p[i])%B)%B;
		//cout << h << ' ' << q[i] << endl;
		sh.insert(h);
	}
	//cout << endl;
	h = 0;
	int ans = 0;
	for (int i = 0; i < n; ++i) {
		h = ((h*A)%B + (ll)(q[i]-'a'+1))%B;
		//cout << h << ' ' << q[i] << endl;
		if (sh.count(h)) {
			ans = max(ans, i);
		}
	}
	ans = n-ans-1;
	cout << ans;
	return 0;
}