N, M = map(int, input().split())
A = list(map(int, input().split()))
A.sort()
ans = 10 ** 18
sm = 0
for i in range(N):
    if i == 0:
        for j in range(M - 1):
            sm += (A[j + 1] - A[j]) ** 2
        ans = sm
        continue
    if i + M - 1 >= N:
        continue
    sm -= (A[i] - A[i - 1]) ** 2
    sm += (A[i + M - 1] - A[i + M - 2]) ** 2
    ans = min(ans, sm)
print(ans)