import java.util.Scanner;

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

        int mark = length - 1;
        for (int i = length - 1; i > -1; i--) {
            if(isPal(arr, i, length - 1) == -1){
                mark = i;
            }
        }
        System.out.println(mark);
    }

    public static int isPal(char[] arr, int a, int b) {
        int end = b;
        for(; a < b; a++, b--) {
            if (arr[a] != arr[b]) {
                return a;
            }
        }
        return -1;
    }
}