n,m=map(int,input().split())
a=list(map(int,input().split()))
a.sort()
x=0
for i in range(1,m):
 x+=(a[i]-a[i-1])**2
res=x
for i in range(m,n):
 x+=(a[i]-a[i-1])**2
 x-=(a[i-m+1]-a[i-m])**2
 res=min(res,x)
print(res)