#ifndef LOCAL
#pragma GCC optimize("O3")
#endif
#include <bits/stdc++.h>
using namespace std;
#define sim template <class c
#define mor > muu & operator<<(
#define ris return *this
#define R22(r) sim> typename enable_if<1 r sizeof(dud<c>(0)),muu&>::type operator<<(c g) {
sim> struct rge {c b, e;};
sim> rge<c> range(c i, c j) {return rge<c>{i, j};}
sim> auto dud(c*r)->decltype(cerr << *r);
sim> char dud(...);
struct muu {
	#ifdef LOCAL
	stringstream a;
	~muu() {cerr << a.str() << endl;}
	R22(<) a << boolalpha << g; ris;}
	R22(==) ris << range(begin(g), end(g));}
	sim mor rge<c> u) {
		a << "[";
		for (c i = u.b; i != u.e; ++i) 
			*this << ", " + 2 * (i == u.b) << *i;
		ris << "]";
	}
	sim, class b mor pair <b,c> r){ris << "(" << r.first << ", " << r.second << ")";}
	#else
	sim mor const c&){ris;}
	#endif
};
#define debug muu() << __FUNCTION__ << "#" << __LINE__ << ": "
#define imie(r...) "[" #r ": " << (r) << "] "
#define range(a, b) "[[" #a ", " #b "): " << range(a, b) << "] "
#define arr(a, i) "[" #a imie(i) ": " << a[i] << "] "
using ll = long long;
using ld = long double;
using pii = pair <int, int>;
const int maxn = 1e6;
void Manacher(const char *s, int n, int r[]) {
	for (int i = 0, m = 0, k = 0, p = 0; i < 2 * n - 1; m = i++ - 1) {
		while (p < k and i / 2 + r[m] != k)
			r[i++] = min(r[m--], (k + 1 - p++) / 2);
		while (k + 1 < n and p > 0 and s[k + 1] == s[p - 1])
			k++, p--;
		r[i] = (k + 1 - p++) / 2;
	}
}
char buff[maxn];
int n;
int proms[maxn];
bool is_pal(int p, int k)
{
	return proms[p + k] >= (k - p + 1) / 2;
}
int main() {
	scanf("%d", &n);
	scanf("%s", buff);
	Manacher(buff, n, proms);
	int res = n-1;
	for(int i = n - 1; i >= 0; --i)
	{
		if(is_pal(i, n-1))
			res = i;
	}
	printf("%d\n", res);
}