N,M=map(int,input().split())
A=list(map(int,input().split()))

A.sort()

score=0
for i in range(1,M):
    score+=(A[i]-A[i-1])**2

LANS=score

for i in range(M,N):
    score+=(A[i]-A[i-1])**2
    score-=(A[i-M+1]-A[i-M])**2
    LANS=min(LANS,score)

print(LANS)