#include <iostream>
#include <string>

using namespace std;

int main() {

    int length;
    scanf("%d ", &length);
    string in;
    cin >> in;
/**
    bool ok = true;
    for (int i = 0; i < length; i++) {
        if (in[i] != in[length - i - 1]) {
            ok = false;
        }
    }

    if (ok) {
        printf("0\n");
        return 0;
    }
*/
    for (int k=0; k<length; ++k) {
        register bool sameShit = true;
        for (register int i = 0; i < (length-k)/2; i++) {
            if (in[i+k] != in[length-i-1]) {
                sameShit = false;
                break;
            }
        }
        if (sameShit) {
            printf("%d\n", k);
            return 0;
        }
    }

    return 0;
}