import collections,sys,math,functools,operator,itertools,bisect,heapq,decimal,string,time,random
#sys.setrecursionlimit(10**9)
#sys.set_int_max_str_digits(0)
#n = int(input())
#
#alist = []
#s = input()
n,m = map(int,input().split())
#for i in range(n):
#    alist.append(list(map(int,input().split())))
alist = list(map(int,input().split()))
alist.sort()
ans = 0
for i in range(m-1):
    ans += (alist[i+1]-alist[i])**2
a = [ans]
for i in range(m-1,n-1):
    ans -= (alist[i-m+1] - alist[i-m+2])**2
    ans += (alist[i]-alist[i+1])**2
    a.append(ans)
print(min(a))