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

const int N = 4e5+5;
const long long A = 911382323;
const long long B = 972663749;
const long long C = 1e9+7;
const long long D = 1e9+9;

#define ll long long

int n;
string s;
long long p[N];
long long r[N];


int sol1(string q) {
	long long h = 0;
	set<long long> sh;	
	for (int i = 0; i < n; ++i) {
		h = (h + ((ll)q[i]*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])%B;
		//cout << h << ' ' << q[i] << endl;
		if (sh.count(h)) {
			ans = max(ans, i);
		}
	}
	return ans;
}

int sol2(string q) {
	long long h = 0;
	set<long long> sh;	
	for (int i = 0; i < n; ++i) {
		h = (h + ((ll)q[i]*r[i])%D)%D;
		//cout << h << ' ' << q[i] << endl;
		sh.insert(h);
	}
	//cout << endl;
	h = 0;
	int ans = 0;
	for (int i = 0; i < n; ++i) {
		h = ((h*C)%D + (ll)q[i])%D;
		//cout << h << ' ' << q[i] << endl;
		if (sh.count(h)) {
			ans = max(ans, i);
		}
	}
	return ans;
}

int main() {
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	r[0] = p[0] = 1;
	for (int i = 1; i < N; ++i) {
		p[i] = (p[i-1]*A)%B;
		r[i] = (r[i-1]*C)%D;
	}
	cin >> n >> s;
	string q(s.rbegin(), s.rend());
	int ans = sol1(q);
	int ans2 = sol2(q);
	string t = s;
	for (int i = ans+1; i < n; ++i) {
		t.push_back(q[i]);
	}
	string u = s;
	for (int i = ans2+1; i < n; ++i) {
		u.push_back(q[i]);
	}
	//cout << t << endl << u << endl;
	string sadf(t.rbegin(), t.rend());
	if (t != sadf) {
		ans = -1;
	}
	string gffg(u.rbegin(), u.rend());
	if (u != gffg) {
		ans2 = -1;
	}
	cout << n-max(ans, ans2)-1;
	
	return 0;
}