#!/usr/bin/env python3
n, k, *P = map(int, open(0).read().split())
p = [(i + 1) / 2 for i in P]
s = [float()]
for i in range(n):
    s.append(s[i] + p[i])
print(max(s[i + k] - s[i] for i in range(n - k + 1))) n, k, *P = map(int, open(0).read().split()) n map(int, open(0).read().split()) map int open(0).read().split() (0).read().split (0).read() (0).read (0) open 0 read split k *P P (i + 1) / 2 for i in P for i in P i P for i in P (i + 1) / 2 i + 1 i 1 2 p = [(i + 1) / 2 for i in P] p [(i + 1) / 2 for i in P] s = [float()] s [float()] float() float for i in range(n):
    s.append(s[i] + p[i]) i range(n) range n s.append(s[i] + p[i]) s.append s append s[i] + p[i] s[i] s i p[i] p i print(max(s[i + k] - s[i] for i in range(n - k + 1))) print max(s[i + k] - s[i] for i in range(n - k + 1)) max s[i + k] - s[i] s[i + k] s i + k i k s[i] s i p = [(i + 1) / 2 for i in P] [(i + 1) / 2 for i in P] p k, *P = map(int, open(0).read().split()) map(int, open(0).read().split()) k n, k, *P = map(int, open(0).read().split()) map(int, open(0).read().split()) n s = [float()] [float()] s
#!/usr/bin/env python3
n, k, *P = map(int, open(0).read().split())
p = [(i + 1) / 2 for i in P]
s = [float()]
for i in range(n):
    s.append(s[i] + p[i])
print(max(s[i + k] - s[i] for i in range(n - k + 1)))
