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