n, m = map(int, input().split())
A = list(map(int, input().split()))
A.sort()

ans = 0
for i in range(m-1):
    ans += (A[i+1] - A[i]) ** 2
    
answer = ans
for i in range(n-m):
    ans -= (A[i+1] - A[i]) ** 2
    ans += (A[i+m] - A[i+m-1]) ** 2
    answer = min (answer, ans)

print(answer)