n, m = map(int, input().split())
a = sorted([*map(int, input().split())])
d = [(v - u) ** 2 for u, v in zip(a, a[1:])]
for i in range(1, n - 1):
    d[i] += d[i - 1]
d = [0] + d
ans = 10 ** 50
for i in range(n - m):
    ans = min(ans, d[i + m - 1] - d[i])
print(ans)