#include <iostream>
#include <string>

using namespace std;

bool isPal(string s){
	for(int i=0,j=s.length()-1;i<=j;i++,j--){
		if (s[i] != s[j]) return false;
	}
	return true;
}

int main(){
	int n;
	string s;

	cin >> n >> s;

	if(isPal(s)){
		cout << 0 << endl;
	}
	else{
		int len = 0;
		for(int i=1;i<n;i++){
			string p = s.substr(i,s.length()-i);
			if(isPal(p)){
				//cout << "Pal: " << p << endl;
				len = s.length() - p.length();
				break;
			}
		}
		cout << len << endl;
	}

	return 0;
}