#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

const int P = 31;
const int M = 1e9+7;

	vector<int> A, B, POT;

int ha(int p, int k) {
	int len = k-p+1;
	return (1ll*A[k]+1ll*M-1ll*(1ll*A[p-1]*POT[len])%M)%M;
}

int hb(int p, int k) {
	int len = k-p+1;
	return (1ll*B[p]+1ll*M-1ll*(1ll*B[k+1]*POT[len])%M)%M;
}

int main(){
	ios_base::sync_with_stdio(0);
	cout.tie(0);
	cin.tie(0);

	int n; cin>>n;
	string s; cin>>s;
	s = ' ' + s;
	A.resize(n+2,0);
	B=A;
	POT=A;
	for(int i=1; i<=n; ++i) A[i]=(1ll*A[i-1]*P + 1ll*(s[i]-'a'+1))%M;
	for(int i=n; i>0; --i) B[i]=(1ll*B[i+1]*P + 1ll*(s[i]-'a'+1))%M;
	POT[0]=1;
	for(int i=1; i<=n; ++i) POT[i]=(1ll*POT[i-1]*P)%M;
	int res = n-1;
	for(int i=1; i<=n; ++i) if(i+i-1>=n) {
		int k = min(i,n-i+1);
		if(ha(i-k+1, i) == hb(i,i+k-1)) res=min(res, i-k);
	}
	for(int i=1; i<=n; ++i) if(i+i>=n) {
		int k = n-i;
		if(ha(i-k+1, i) == hb(i+1,i+k)) res=min(res, i-k);
	}
	cout<<res<<"\n";
	return 0;
}