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