N,M=map(int,input().split())
A=list(map(int,input().split()))
A.sort()
D=[0]+[(b-a)**2 for a,b in zip(A,A[1:])]
for i in range(1,N):
    D[i]+=D[i-1]
ans=min(D[i+M-1]-D[i] for i in range(N-M+1))
print(ans)