import sys
input = sys.stdin.readline

n, m = map(int, input().split())
A = list(map(int, input().split()))

A.sort()
ans = 10**18
res = 0
for i in range(1, n):
    res += (A[i] - A[i - 1])**2
    if i >= m - 1:
        ans = min(ans, res)
        res -= (A[i - m + 2] - A[i - m + 1])**2
print(ans)