N, K = map(int, input().split())
P = list(map(int, input().split()))

a = [0] * (N - K + 1)
a[0] = sum(P[:K])
for i in range(1, N - K + 1):
    a[i] = a[i - 1] - P[i - 1] + P[i + K - 1]
    
print((max(a) + K) / 2) N, K = map(int, input().split()) N map(int, input().split()) map int input().split() ().split () input split K P = list(map(int, input().split())) P list(map(int, input().split())) list map(int, input().split()) map int input().split() ().split () input split a = [0] * (N - K + 1) a [0] * (N - K + 1) [0] 0 N - K + 1 N - K N K 1 a[0] = sum(P[:K]) a[0] a 0 sum(P[:K]) sum P[:K] P :K K for i in range(1, N - K + 1):
    a[i] = a[i - 1] - P[i - 1] + P[i + K - 1]
     i range(1, N - K + 1) range 1 N - K + 1 N - K N K 1 a[i] = a[i - 1] - P[i - 1] + P[i + K - 1] a[i] a i a[i - 1] - P[i - 1] + P[i + K - 1] a[i - 1] - P[i - 1] a[i - 1] a i - 1 i 1 P[i - 1] P i - 1 i 1 P[i + K - 1] P i + K - 1 i + K i K 1 print((max(a) + K) / 2) print (max(a) + K) / 2 max(a) + K max(a) max a K 2 a = [0] * (N - K + 1) [0] * (N - K + 1) a N, K = map(int, input().split()) map(int, input().split()) N P = list(map(int, input().split())) list(map(int, input().split())) P K = map(int, input().split()) map(int, input().split()) K
N, K = map(int, input().split())
P = list(map(int, input().split()))

a = [0] * (N - K + 1)
a[0] = sum(P[:K])
for i in range(1, N - K + 1):
    a[i] = a[i - 1] - P[i - 1] + P[i + K - 1]
    
print((max(a) + K) / 2)