Problem:
Score : 400 points

Problem Statement

We have N points in a two-dimensional plane.

The coordinates of the i-th point (1 \leq i \leq N) are (x_i,y_i).

Let us consider a rectangle whose sides are parallel to the coordinate axes that contains K or more of the N points in its interior.

Here, points on the sides of the rectangle are considered to be in the interior.

Find the minimum possible area of such a rectangle.

Constraints

2 \leq K \leq N \leq 50

-10^9 \leq x_i,y_i \leq 10^9 (1 \leq i \leq N)

x_i≠x_j (1 \leq i<j \leq N)

y_i≠y_j (1 \leq i<j \leq N)

All input values are integers. (Added at 21:50 JST)

Input

Input is given from Standard Input in the following format:

N K
x_1 y_1
:
x_{N} y_{N}

Output

Print the minimum possible area of a rectangle that satisfies the condition.

Sample Input 1

4 4
1 4
3 3
6 2
8 1

Sample Output 1

21

One rectangle that satisfies the condition with the minimum possible area has the following vertices: (1,1), (8,1), (1,4) and (8,4).

Its area is (8-1) × (4-1) = 21.

Sample Input 2

4 2
0 0
1 1
2 2
3 3

Sample Output 2

1

Sample Input 3

4 3
-1000000000 -1000000000
1000000000 1000000000
-999999999 999999999
999999999 -999999999

Sample Output 3

3999999996000000001

Watch out for integer overflows.

Solution in Python (3.4.3) (judge verdict: Time Limit Exceeded)

def main():
    N, K = map(int, input().split())
    XY = [tuple(map(int, input().split())) for _ in range(N)]
    XY.sort()
    XY = tuple(XY)

    def count(x_min, x_max, y_min, y_max, i, j):
        OK = 0
        # NG = 0
        for m in XY[i:j + 1]:
            if y_min <= m[1] <= y_max:
                OK += 1
        if OK >= K:
            return True
        return False

    ans = 10 ** 20
    for i, val_i in enumerate(XY[:N - 1]):
        a = val_i[0]
        for j in range(i + K - 1, N):
            b = XY[j][0]
            e = b - a
            # print (e, i, j)
            for k in XY:
                c = k[1]
                for l in XY:
                    d = l[1]
                    if c < d:
                        if count(a, b, c, d, i, j):
                            # print ('A')
                            ans = min(ans, e * (d - c))
    print (ans)
    return

if __name__ == '__main__':
    main()