n, m = map(int, input().split())
A = list(map(int, input().split()))
A.sort()
if m == 1:
    print(0)
    exit()

B = [(A[i + 1] - A[i]) ** 2 for i in range(n - 1)]

m -= 1
tot = sum(B[:m])
ans = tot
for i in range(m, n - 1):
    tot += B[i] - B[i - m]
    ans = min(ans, tot)

print(ans)