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: Wrong Answer)

n, k = map(int, input().split())
xy = []
for _ in range(n):
  xy.append(tuple(map(int, input().split())))
xy = list(sorted(xy, key=lambda x: x[0]))
mins = None

for i in range(0, n-k+1):
  _xy = xy[i:i+k]
  if mins is None:
    mins = (_xy[-1][0] - _xy[0][0]) * (max(k[1] for k in _xy) - min(k[1] for k in _xy))
  elif mins > (_xy[-1][0] - _xy[0][0]) * (max(k[1] for k in _xy) - min(k[1] for k in _xy)):
    mins = (_xy[-1][0] - _xy[0][0]) * (max(k[1] for k in _xy) - min(k[1] for k in _xy))

xy = list(sorted(xy, key=lambda x: x[1]))
for i in range(0, n-k+1):
  _xy = xy[i:i+k]
  if mins > (_xy[-1][1] - _xy[0][1]) * (max(k[0] for k in _xy) - min(k[0] for k in _xy)):
    mins = (_xy[-1][1] - _xy[0][1]) * (max(k[0] for k in _xy) - min(k[0] for k in _xy))

print(mins)