#include <bits/stdc++.h>


#define MAX 500000

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

    scanf("%d ", &count);

    fgets(str, MAX, stdin);

    for(int i = count - 1; i > 0; i--){
        if(str[i] == str[i - 1]){
            pom = 3;
            for(int j = i + 1; j < count; j++){
                if(str[j - pom] != str[j]){
                    p = true;
                    break;
                }
                pom++;
            }
            if(!p){
                res = count - 2 * (count - i);
                break;
            }

        }
        if(i > 1 && str[i] == str[i - 2]){
            pom = 4;
            for(int j = i + 1; j < count; j++){
                if(str[j - pom] != str[j]){
                    p = true;
                    break;
                }
                pom++;
            }
            if(!p){
                res = count - 2 * (count - i);
                break;
            }
        }
    }
    if(res == -1){
        res = count - 1;
    }


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


    return 0;
}