uva1432

#include <iostream>
#include <istream>
#include <sstream>
#include <vector>
#include <stack>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <queue>
#include <cstring>
#include <unordered_map>
#include <unordered_set>
#include <algorithm>
#include <numeric>
#include <chrono>
#include <ctime>
#include <cmath>
#include <cctype>
#include <string>
#include <cstdio>
#include <iomanip>


#include <thread>
#include <mutex>
#include <condition_variable>
#include <functional>
#include <iterator>
using namespace std;
const int maxn = 5007, INF = 0x3f3f3f3f;
const double PI = acos(-1.0);
int n, k, arr[maxn];
struct Node {
    
	int x, y, tot;
	double r, at;
	bool operator<(const Node& input) {
    
		return r < input.r;
	}
	void Get() {
    
		cin >> x >> y;
		r = sqrt(x * x * 1.0 + y * y * 1.0);
		at = atan2(y, x);
		tot = 1;
	}
}node[maxn];

bool cmp(const Node& a, const Node& b) {
    
	return a.at < b.at;
}

bool LessEqual(int i, int j) {
    
	if (node[i].r < node[j].r || fabs(node[i].r - node[j].r) < 1e-9) {
    
		return true;
	}
	return false;
}
double GetResult() {
    
	if (k == 0) return 0;
	double ans = INF;
	sort(node, node + n, cmp);
	set<double> mset;
	for (int i = 0; i < n; i++) {
    
		if (node[i].tot < k)continue;
		double angle = 2 * PI, r = node[i].r;
		if (mset.count(r))continue;
		mset.insert(r);
		int cnt = 0;
		
		for (int j = 0; j < n; j++) {
    
			if (LessEqual(j,i)) {
    
				arr[cnt++] = j;
				if (cnt >= k) {
    
					angle = min(angle, node[arr[cnt - 1]].at - node[arr[cnt - k]].at);
				}
			}
		}
		if (cnt < k) continue;
		for (int j = 0; j < k; j++) {
    
			angle = min(angle, node[arr[j]].at - node[arr[cnt + j - k + 1]].at + 2 * PI);
		}
		ans = min(ans, r * r * angle / 2);
	}
	return ans;
}

int main()
{
    
	int kCase = 1;
	while (cin >> n >> k && n + k) {
    
		for (int i = 0; i < n; i++) {
    
			node[i].Get();
		}
		sort(node, node + n);
		for (int i = 1; i < n; i++) {
    
			node[i].tot += node[i - 1].tot;
		}
		cout << "Case #" << kCase++ << ": " << fixed << setprecision(2) << GetResult() << endl;
	}
	return 0;
}