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 Rust (1.15.1) (judge verdict: Accepted)

#![allow(non_snake_case)]

fn main() {
    let stdin = std::io::stdin();
    let mut stdin = my::io::InputReader::new(stdin.lock());

    let N: usize = stdin.read();
    let K: usize = stdin.read();
    let (x, y): (Vec<i32>, Vec<i32>) = (0..N).map(|_| (stdin.read::<i32>(), stdin.read::<i32>())).unzip();
    let mut acc = vec![vec![0_i32; N + 1]; N + 1];
    let mut xi: Vec<_> = (0..N).map(|i| (x[i], i)).collect();
    let mut yi: Vec<_> = (0..N).map(|i| (y[i], i)).collect();
    xi.sort();
    yi.sort();
    let mut rank_x = vec![0; N];
    let mut rank_y = vec![0; N];
    for i in 0..N {
        rank_x[xi[i].1] = i;
        rank_y[yi[i].1] = i;
    }
    for k in 0..N {
        let i = rank_x[k];
        let j = rank_y[k];
        acc[i + 1][j + 1] += 1;
    }
    for i in 0..N + 1 {
        for j in 0..N {
            acc[i][j + 1] += acc[i][j];
        }
    }
    for i in 0..N {
        for j in 0..N + 1 {
            acc[i + 1][j] += acc[i][j];
        }
    }
    let mut area_min = std::u64::MAX;
    for i1 in 0..N {
        for i2 in i1 + 1..N {
            for j1 in 0..N {
                for j2 in j1 + 1..N {
                    let count_interior = (acc[i2 + 1][j2 + 1] -acc[i2 + 1][j1] - acc[i1][j2 + 1] + acc[i1][j1]) as usize;
                    if count_interior >= K {
                        let area = (xi[i2].0 - xi[i1].0) as u64 * (yi[j2].0 - yi[j1].0) as u64;
                        area_min = std::cmp::min(area_min, area);
                    }
                }
            }
        }
    }
    println!("{}", area_min);
}

#[allow(dead_code, unused_must_use)]
mod my {
    pub mod io {
        use std::io::{BufRead, ErrorKind, Result};
        use std::str::{FromStr, from_utf8};
        use std::fmt::Debug;

        pub fn read_word<R: BufRead>(r: &mut R, buf: &mut Vec<u8>)
                                              -> Result<usize> {
            let mut read = 0;
            loop {
                let (done, used) = {
                    let available = match r.fill_buf() {
                        Ok(n) => n,
                        Err(ref e) if e.kind() == ErrorKind::Interrupted => continue,
                        Err(e) => return Err(e)
                    };
                    match available.iter().position(|&x| x == b'\n' || x == b' ') {
                        Some(i) => {
                            buf.extend_from_slice(&available[..i]);
                            (true, i + 1)
                        }
                        None => {
                            buf.extend_from_slice(available);
                            (false, available.len())
                        }
                    }
                };
                r.consume(used);
                read += used;
                if done || used == 0 {
                    return Ok(read);
                }
            }
        }

        pub struct InputReader<R: BufRead> {
            reader: R,
            buf: Vec<u8>,
        }

        impl<R: BufRead> InputReader<R> {
            pub fn new(reader: R) -> InputReader<R> {
                InputReader {
                    reader: reader,
                    buf: Vec::<u8>::new(),
                }
            }

            pub fn read_word(&mut self) {
                read_word(&mut self.reader, &mut self.buf);
            }
            
            pub fn read<T>(&mut self) -> T
                where T: FromStr,
                      T::Err: Debug
            {
                self.buf.clear();
                self.read_word();
                from_utf8(&self.buf).unwrap().trim().parse().unwrap()
            }
        }
    }
}