n, m = [int(x) for x in input().split()]
a = [int(x) for x in input().split()]
a.sort()
d = []
for i in range(1, n):
	d.append((a[i] - a[i-1]) ** 2)
ans = 10 ** 19
s = sum(d[:m-1])
for i in range(n - m):
	s += d[i+m-1] - d[i]
	ans = min(s, ans)
print(ans)