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

A = sorted(A)

s = [0] * N
for i in range(N-1):
    s[i+1] = s[i] + (A[i+1] - A[i]) ** 2

ans = A[-1] ** 2
for i in range(N):
    if i+M-1 >= N:
        break
    ans = min(ans, s[i+M-1] - s[i])
# print(s)
print(ans)