#include <algorithm>
#include <iostream>
#include <vector>
using namespace std;

const int INF = 1000000000;
const int LIM = 2000005;

int R, C, K;
string G[LIM];

int solve() {
  cin >> R >> C >> K;
  for (int i = 1; i <= R; i++) {
    cin >> G[i];
  }
  vector<int> nb(LIM);
  for (int j = 0; j < C; j++) {
    int tot = 0;
    for (int i = 1; i <= R; i++) {
      tot += G[i][j] == 'X';
    }
    int curr = 0;
    for (int i = 0; i <= R + 1; i++) {
      bool isX = 1 <= i && i <= R && G[i][j] == 'X';
      curr += isX;
      if (isX || curr > K - 1 || tot - curr > R - K) {
        nb[i]++;
      }
    }
  }
  int ans = INF;
  for (int i = 0; i <= R + 1; i++) {
    ans = min(ans, abs(i - K) + nb[i]);
  }
  return ans;
}

int main() {
  int T;
  cin >> T;
  for (int t = 1; t <= T; t++) {
    cout << "Case #" << t << ": " << solve() << endl;
  }
  return 0;
}