#include<bits/stdc++.h>
using namespace std;
string s,a="",b="";
int n,ans;
int main(){
	cin>>n>>s;
	for(int i=n-1;i>=0;i--){
		a+=s[i];
		b=s[i]+b;
		if(a==b)ans=i;
	}
	cout<<ans;
	return 0;
}

$1\le N\le4\times 10^5$