N, K = map(int, input().split())
P = list(map(int, input().split()))
A = [(p + 1) / 2 for p in P]
B = [0 for i in range(N)]
B[0] = A[0]
for i in range(1, N):
    B[i] = B[i - 1] + A[i]
ans = 0
for i in range(K - 1, N):
    if i == K - 1:
        a = B[i]
    else:
        a = B[i] - B[i - K]
    if ans < a:
        ans = a
print(ans) 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 (p + 1) / 2 for p in P for p in P p P for p in P (p + 1) / 2 p + 1 p 1 2 A = [(p + 1) / 2 for p in P] A [(p + 1) / 2 for p in P] 0 for i in range(N) for i in range(N) i range(N) range N for i in range(N) 0 B = [0 for i in range(N)] B [0 for i in range(N)] B[0] = A[0] B[0] B 0 A[0] A 0 for i in range(1, N):
    B[i] = B[i - 1] + A[i] i range(1, N) range 1 N B[i] = B[i - 1] + A[i] B[i] B i B[i - 1] + A[i] B[i - 1] B i - 1 i 1 A[i] A i ans = 0 ans 0 for i in range(K - 1, N):
    if i == K - 1:
        a = B[i]
    else:
        a = B[i] - B[i - K]
    if ans < a:
        ans = a i range(K - 1, N) range K - 1 K 1 N if i == K - 1:
        a = B[i]
    else:
        a = B[i] - B[i - K]
     i == K - 1 i K - 1 K 1 a = B[i] a B[i] B i a = B[i] - B[i - K] a B[i] - B[i - K] B[i] B i B[i - K] B i - K i K if ans < a:
        ans = a ans < a ans a ans = a ans a print(ans) print ans A = [(p + 1) / 2 for p in P] [(p + 1) / 2 for p in P] A B = [0 for i in range(N)] [0 for i in range(N)] B K = map(int, input().split()) map(int, input().split()) K a = B[i] - B[i - K] B[i] - B[i - K] a ans = 0 0 ans P = list(map(int, input().split())) list(map(int, input().split())) P N, K = map(int, input().split()) map(int, input().split()) N ans = a a ans a = B[i] B[i] a
N, K = map(int, input().split())
P = list(map(int, input().split()))
A = [(p + 1) / 2 for p in P]
B = [0 for i in range(N)]
B[0] = A[0]
for i in range(1, N):
    B[i] = B[i - 1] + A[i]
ans = 0
for i in range(K - 1, N):
    if i == K - 1:
        a = B[i]
    else:
        a = B[i] - B[i - K]
    if ans < a:
        ans = a
print(ans)
