#include <bits/stdc++.h>


#define MAX 500000

int main()
{
    int count, res = -1;
    char str[MAX];
    int pom = 1;

    scanf("%d ", &count);

    fgets(str, MAX, stdin);

    for(int i = 0; i < count; i++){
        for(int j = i; j < count - pom; j++){
            if(str[j] != str[count - pom]){
                pom = 1;
                break;
            }
            pom++;
            if(j == count - pom || j == count - pom - 1){
                res = i;
            }
        }
        if(res > -1){
            break;
        }
    }
    if(res == -1){
        res = count - 1;
    }

    printf("%d\n", res);


    return 0;
}