#include <bits/stdc++.h>

using namespace std;

void input(string f)
{
	string one = f + ".in";
	string two = f + ".out";

	freopen(one.c_str(), "r", stdin);
	freopen(two.c_str(), "w", stdout);	
}

const long long N = 57;
const long long inf = 1e18;

pair<long long, long long> p[N];
long long curr_idx;

long long area(pair<long long, long long> p1, pair<long long, long long> p2, pair<long long, long long> p3){
	long long x1 = p2.first - p1.first;
	long long y1 = p2.second - p1.second;
	long long x2 = p3.first - p1.first;
	long long y2 = p3.second - p1.second;

	return x1 * y2 - x2 * y1;
}

bool cmp(pair<long long, long long> lvalue, pair<long long, long long> rvalue){
	if(area(p[curr_idx], lvalue, rvalue) > 0){
		return true;
	}

	if(area(p[curr_idx], lvalue, rvalue) == 0){
		return lvalue < rvalue;
	}

	return false;
}

long long dp[N][N][N][N];

int main(){
	ios::sync_with_stdio(false);
	cin.tie(NULL);

	input("farm");

	long long n, k;

	cin >> n >> k;

	for(long long i = 0; i < n; i++){
		cin >> p[i].first >> p[i].second;
	}

	for(long long i = 0; i < n; i++){
		for(long long j = i + 1; j < n; j++){
			for(long long left = 1; left <= k; left++){
				dp[i][j][left][n] = -inf;
			}
			dp[i][j][0][n] = 0;
		}
	}

	long long res = 0;

	for(long long i = 0; i <= n - k; i++){
		sort(p, p + n);
		curr_idx = i;

		sort(p + i + 1, p + n, cmp);

		//for(long long j = i; j < n; j++){
		//	cout << "point " << j << ": " << p[j].first << " " << p[j].second << "\n";
		//}

		for(long long pr1 = n - 2; pr1 >= i; pr1--){
			for(long long pr2 = n - 1; pr2 >= pr1 + 1; pr2--){
				for(long long left = 0; left <= k - 2; left++){
					for(long long j = n - 1; j >= pr2 + 1; j--){
						dp[pr1][pr2][left][j] = dp[pr1][pr2][left][j + 1];

						if(area(p[pr1], p[pr2], p[j]) > 0 && left > 0){
							//cout << area(p[i], p[pr2], p[j]) << " area "<< dp[pr2][j][left - 1][j+1] << "\n";
							dp[pr1][pr2][left][j] = max(dp[pr1][pr2][left][j], area(p[i], p[pr2], p[j]) + dp[pr2][j][left - 1][j+1]);
						}

						//cout << dp[pr1][pr2][left][j] << " = " << pr1 << " " << pr2 << " " << left << " " << j << "\n"; 
					}
				}
			}
		}

		for(long long pr2 = n - 1; pr2 >= i + 1; pr2--){
			res = max(res, dp[i][pr2][k-2][pr2 + 1]);
			//cout << dp[i][pr2][k-2][pr2 + 1] << " =  " << p[i].first << " " << p[i].second << ", " << p[pr2].first << " " << p[pr2].second << "\n";  
		}
	}

	if(res <= 0){
		cout << "-1\n";

		return 0;
	}

	cout << res << "\n";

	return 0;
}