n, m = map(int, input().split())
a = sorted([*map(int, input().split())])
ans, res = 10 ** 50, 0
for i, v in enumerate(a):
    if i > 0:
        res += (v - p) ** 2
        if i >= m:
            res -= (a[i - m + 1] - a[i - m]) ** 2
    if i >= m - 1:
        ans = min(ans, res)
    p = v
print(ans)