#include <iostream>
#include <string>
#include <algorithm>

using namespace std;

string str;
string c;
bool isPalindrome()  {

    int div_point;
    string eleje;
    string vege;

    if ((c.length()) % 2 == 0) {
        div_point = c.length() / 2;
        eleje = c.substr(0, div_point);
        vege = c.substr(div_point);

    } else {
        div_point = c.length() / 2 + 1;
        eleje = c.substr(0, div_point);
        vege = c.substr(div_point - 1);
    }

    //cout << div_point << endl;
    reverse(vege.begin(), vege.end());
    //cout << c << endl;
    //cout << eleje << endl << vege << endl;
    //cout << endl;
    return (vege == eleje);
}

int main() {

    int n;
    cin >> n >> str;
    c = str;

    while (c.find(str[n - 1]) != string::npos) {
        c = c.substr(c.find(str[n - 1]));
        if (isPalindrome()) {
            cout << n - c.length() << endl;
            break;
        }
        c = c.substr(1);

    }


}