#include <algorithm>
#include <iostream>
#include <vector>
#include <string>

using namespace std;

typedef vector <int> vi;

void init(string& P, vi& b) {
	int i = 0, j = -1; b[0] = -1;
	while(i < P.size()) {
		while(j > -1 && P[i] != P[j]) j = b[j];
		b[++i] = ++j;
	}
	
	return ;
}

int kmp(string& T, string& P, vi& b) {
	int i = 0, j = 0;
	while(i < T.size()) {
		while(j > -1 && T[i] != P[j]) j = b[j];
		++i; ++j;
	}
	
	return i - j;
}

int main() {
	int n; cin >> n;
	string li, ne; cin >> li;
	vi b(li.size() + 1);
	ne = li;
	reverse(ne.begin(), ne.end());
	init(ne, b);
	cout << kmp(li, ne, b);
	return 0;
}