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

const int N = 4e5+1;
const long long A = 911382323;
const long long B = 972663749;

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 = n-1; i >= 0; --i) {
		h = (h*A+(long long)(s[i]))%B;
		//cout << h << ' ' << s[i] << endl;
		sh.insert(h);
	}
	h = 0;
	//cout << endl;
	for (int i = 0; i < n; ++i) {
		h += (p[i]*(long long)(q[i]))%B;
		//cout << h << ' ' << q[i] << endl;
		if (sh.count(h) == 0) {
			cout << (n-i);
			return 0;
		}
	}
	cout << 0;
	return 0;
}