#include "bits/stdc++.h"
using namespace std;

int n;

int score(string s) {
    int res = 0;
    int len = s.size();
    for (int i = 0; i < len / 2; i ++) {
        if (s[i] != s[len - i - 1]) res += 1;
    }
    return res;
}

int main() {
    cin >> n;
    for (int i = 1; i <= n; i ++) {
        int n, k;
        cin >> n >> k;
        string s;
        cin >> s;

        printf("Case #%d: %d\n", i, abs(score(s) - k));

    }
    return 0;
}