#include <bits/stdc++.h>
#define st first
#define nd second
#define fi first
#define se second
#define pb push_back
#define ps(v) cout << v << " "
#define pln(v) cout << v << "\n"
#define entr cout << "\n"

using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<ll, ll> pll;


int main() {
	ios_base::sync_with_stdio(0);
	int n; string a;
	cin >> n >> a;
	string c;
	for (int i = 0; i < n; i++) {
		c.push_back(a[i]);
		c.push_back('#');
	}
	c.push_back('$');
	int s = c.size(); vector <int> P(s);
	for (int i = 0, k = 0; i < s; i++) {
		if (k+P[k] > i) {
			P[i] = max(1, min(P[2*k-i], k+P[k]-i));
		}
		while (P[i] <= i && c[i+P[i]] == c[i-P[i]]) {
			P[i]++;
		}
		if (i+P[i] > k+P[k]) {
			k = i;
		}
		//cout << P[i] << " ";
	}
	//cout <<endl;
	int ans = n-1;
	//cout << s <<endl;
	for (int i = 0; i < s-1; i++) {
		//cout << i << " " << i+P[i] << " " << s <<endl;
		if (c[i] == '#') {
			//cout << i << " " << c[i] << " " << i+P[i] << " " << (i-P[i]+2)/2 <<endl;
			if (i+P[i] >= s-2) {
				ans = min(ans, (i-P[i]+2) / 2);
			} 
		}
		else {
			//cout << i << " " << c[i] << " " << i+P[i] << " " << (i-P[i]+2)/2 <<endl;
			if (i+P[i] >= s-1) {
				ans = min(ans, (i-P[i] + 2) / 2);
			} 
		}
		//cout << ans <<endl;
	}
	cout << ans <<endl;
	return 0;
}