#include <bits/stdc++.h>
using i64 = long long;

const int maxn = 1e6 + 5;
const i64 mod = 127237991;
const i64 p = 131;
char s[maxn];
int n;
i64 hash[maxn],pw[maxn];

bool check(int x,int y,int l,int r) {
	return ((hash[y] - hash[x - 1] * pw[y - x + 1] % mod + mod) % mod) == ((hash[r] - hash[l - 1] * pw[r - l + 1] % mod + mod) % mod);
}

int main() {
	freopen("prefixuffix.in","r",stdin);
	freopen("prefixuffix.out","w",stdout);
	scanf("%d %s",&n,s + 1);
	pw[0] = 1;
	hash[0] = 0;
	for(int i = 1;i <= n;++ i) {
		pw[i] = (pw[i - 1] * p) % mod;
		hash[i] = (hash[i - 1] * p + (unsigned)s[i]) % mod;
	}
	for(int i = n / 2;i;-- i) {
		if(check(1 , i , n - i + 1 , n)) {
			printf("%d\n",i);
			return 0;
		}
		for(int k = 1;k < i;++ k) {
			if(check(1 , k , n - k + 1 , n)&&check(k + 1 , i , n - i + 1 , n - k)) {
				printf("%d\n",i);
				return 0;
			}
		}
	}
	puts("0");
	return 0;
}