题解 | 画展布置

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

# Algo
arr.sort()
cost = [arr[i]**2-arr[i-1]**2 for i in range(1, N)]
m, n = M-1, N-1
minL = L = sum(cost[i] for i in range(m))  # Init
for i in range(m, n):
    L = L - cost[i-m] + cost[i]
    minL = min(minL, L)

# Output
print(minL)