package main

import . "fmt"
import . "os"
import bf "bufio"
import . "slices"

func main() {
	rd:=bf.NewReader(Stdin)
	var n,m int
	Fscan(rd,&n,&m)
	a:=make([]int64,n)
	for i:=range a {
		Fscan(rd,&a[i])
	}
	Sort(a)
	var x,y int
	var ans,s int64
	for {
		if x-y < m {
			x++
			if x>=n {
				break
			}
			s+=(a[x]-a[x-1])*(a[x]-a[x-1])
		} else {
			if ans==0||s<ans {
				ans=s
			}
			y++
			s-=(a[y]-a[y-1])*(a[y]-a[y-1])
		}
	}
	Println(ans)
}