from collections import *

N, M = map(int, input().split())
A = sorted(list(map(int, input().split())))
Q = deque()
now = 0
for i in range(M):
    Q.append(A[i])
    if len(Q) >= 2:
        now += (Q[-1] - Q[-2])**2
ans = now
for i in range(M, N):
    Q.append(A[i])
    now += (Q[-1] - Q[-2]) ** 2
    now -= (Q[0] - Q[1]) ** 2
    Q.popleft()
    ans = min(ans, now)

print(ans)