#include <bits/stdc++.h>
#define FOR(i, n) for(int i = 0; i < (n); ++i)
#define REP(i, a, b) for(int i = (a); i < (b); ++i)
#define TRAV(i, a) for(auto &i : (a))
#define X first
#define Y second
#define MP std::make_pair
#define PR std::pair
#define SZ(x) ((int)(x).size())
typedef long long ll;
typedef std::pair<int, int> PII;
typedef std::vector<int> VI;

// sh - parzystosc
// 0 - parzyste
// aaaa 0  [0, 1, 2, 1]    1 [1, 2, 2, 1]
std::vector<int> manacher(const std::string &w, int sh){
	int n = SZ(w);
	VI p(n);
	int g = 0;
	p[0] = sh;
	REP(i, 1, n){
		if(2*g-i >= 0) p[i] = std::max(std::min(p[2*g-i], p[g]+g-i), 0);
		else p[i] = 0;
		while(i-p[i]-1+sh >= 0 && i+p[i] < n && w[i+p[i]] == w[i-p[i]-1+sh]) p[g=i]++;
	}
	return p;
}

int main(){
	std::ios_base::sync_with_stdio(false);
	std::cin.tie(0);
	int n;
	std::cin >> n;
	std::string s;
	std::cin >> s;
	auto par = manacher(s, 0);
	auto np = manacher(s, 1);
	int best = 1000000000;
	FOR(i, n){
		if(np[i] == n-i){
			best = std::min(best, i+1 - np[i]);
		}
	}
	FOR(i, n){
		if(par[i] == n-i){
			best = std::min(best, i-par[i]);
		}
	}
	std::cout << best;

	return 0;
}