import java.util.Scanner;

public class Abb {
    public static void main(String[] args) {
        var sc = new Scanner(System.in);
        sc.nextLine();
        var arr = sc.nextLine().toCharArray();

        for (int i = 0; i < arr.length; i++) {
            if (isPal(arr, i, arr.length - 1)) {
                System.out.println(i);
                break;
            }
        }

    }

    public static boolean isPal(char[] arr, int a, int b) {
        for(; a < b; a++, b--) {
            if (arr[a] != arr[b]) {
                return false;
            }
        }
        return true;
    }
}