#include <bits/stdc++.h>
using namespace std;
using ll = long long;

int N, K, x[55], y[55];
int main() {
  cin >> N >> K;
  for (int i = 0; i < N; i++) cin >> x[i] >> y[i];
  ll ret = 1LL << 62;
  for (int i = 0; i < N; i++) {
    for (int j = 0; j < N; j++) {
      for (int k = 0; k < N; k++) {
        for (int l = 0; l < N; l++) {
          if (x[i] <= x[j] && y[k] <= y[l]) {
            int cnt = 0;
            for (int p = 0; p < N; p++) {
              if (x[i] <= x[p] && x[p] <= x[j] && y[k] <= y[p] && y[p] <= y[l])
                cnt++;
            }
            if (cnt >= K) ret = min(ret, 1LL * (x[j] - x[i]) * (y[l] - y[k]));
          }
        }
      }
    }
  }
  cout << ret << endl;
  return 0;
}
