N, M = map(int, input().split())
A = list(map(int, input().split()))
A.sort()

# N個からM個選ぶ
B = [0]
for i in range(N - 1):
    pos, nex = A[i], A[i + 1]
    B.append((nex - pos)**2)

for i in range(N - 1):
    B[i + 1] += B[i]

ans = 1e18
for i in range(M - 1, N):
    sub = B[i] - B[i - M + 1]
    if sub < ans:
        ans = sub
print(ans)