Buggy python submission (verdict: Time Limit Exceeded):
# -*- coding: utf-8 -*-

#def f(x):
#    if x == 1:
#        return 1
#    else:
#        return f(x-1) + x

[N, K] = [int(i) for i in input().split()]
P = [int(i) for i in input().split()]

max_index = 0
max_sum = 0
for i in range(len(P)-(K-1)):
    sum_P = sum(P[i:i+K])
    if sum_P > max_sum:
        max_sum = sum_P
        max_index = i

#print(max_sum)
#print(max_index)

# 隣接したK個のリスト
kk = P[max_index:max_index+K]

# kの期待値を計算
#max_kk = max(kk)
#dp = [0]
#for i in range(1, max_kk+1):
#    dp.append(dp[i-1] + i)
#print(dp)

ans = 0
for k in kk:
    for i in range(1, k+1):
        ans += i/k
        #ans += f(k)/k

print(ans)

Fixed submission:
# -*- coding: utf-8 -*-

#def f(x):
#    if x == 1:
#        return 1
#    else:
#        return f(x-1) + x

[N, K] = [int(i) for i in input().split()]
P = [int(i) for i in input().split()]

max_index = 0
now_sum = sum(P[:K])
max_sum = now_sum
for i in range(1, len(P)-(K-1)):
    now_sum -= P[i-1]
    now_sum += P[i+K-1]
    #sum_P = sum(P[i:i+K])
    if now_sum > max_sum:
        max_sum = now_sum
        max_index = i

#print(max_sum)
#print(max_index)

# 隣接したK個のリスト
kk = P[max_index:max_index+K]

# kの期待値を計算
max_kk = max(kk)
dp = [0]
for i in range(1, max_kk+1):
    dp.append(dp[i-1] + i)
#print(dp)

ans = 0
for k in kk:
    ans += dp[k]/k

print(ans)

Buggy python submission (verdict: Runtime Error):
# -*- coding: utf-8 -*-

def f(x):
    if x == 1:
        return 1
    else:
        return f(x-1) + x

[N, K] = [int(i) for i in input().split()]
P = [int(i) for i in input().split()]

max_index = 0
max_sum = 0
for i in range(len(P)-(K-1)):
    sum_P = sum(P[i:i+K])
    if sum_P > max_sum:
        max_sum = sum_P
        max_index = i

#print(max_sum)
#print(max_index)

# 隣接したK個のリスト
kk = P[max_index:max_index+K]

# kの期待値を計算
#max_kk = max(kk)
#dp = [0]
#for i in range(1, max_kk+1):
#    dp.append(dp[i-1] + i)
#print(dp)

ans = 0
for k in kk:
    ans += f(k)/k

print(ans)

Fixed submission:
# -*- coding: utf-8 -*-

#def f(x):
#    if x == 1:
#        return 1
#    else:
#        return f(x-1) + x

[N, K] = [int(i) for i in input().split()]
P = [int(i) for i in input().split()]

max_index = 0
now_sum = sum(P[:K])
max_sum = now_sum
for i in range(1, len(P)-(K-1)):
    now_sum -= P[i-1]
    now_sum += P[i+K-1]
    #sum_P = sum(P[i:i+K])
    if now_sum > max_sum:
        max_sum = now_sum
        max_index = i

#print(max_sum)
#print(max_index)

# 隣接したK個のリスト
kk = P[max_index:max_index+K]

# kの期待値を計算
max_kk = max(kk)
dp = [0]
for i in range(1, max_kk+1):
    dp.append(dp[i-1] + i)
#print(dp)

ans = 0
for k in kk:
    ans += dp[k]/k

print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
# -*- coding: utf-8 -*-

[N, K] = [int(i) for i in input().split()]
P = [int(i) for i in input().split()]

max_index = 0
max_sum = 0
for i in range(len(P)-(K-1)):
    sum_P = sum(P[i:i+K])
    if sum_P > max_sum:
        max_sum = sum_P
        max_index = i

#print(max_sum)
#print(max_index)

# 隣接したK個のリスト
kk = P[max_index: max_index+K]

# kの期待値を計算
max_kk = max(kk)
dp = [0]
for i in range(1, max_kk+1):
    dp.append(dp[i-1] + i)
#print(dp)

ans = 0
for k in kk:
    ans += dp[k]/k

print(ans)

Fixed submission:
# -*- coding: utf-8 -*-

#def f(x):
#    if x == 1:
#        return 1
#    else:
#        return f(x-1) + x

[N, K] = [int(i) for i in input().split()]
P = [int(i) for i in input().split()]

max_index = 0
now_sum = sum(P[:K])
max_sum = now_sum
for i in range(1, len(P)-(K-1)):
    now_sum -= P[i-1]
    now_sum += P[i+K-1]
    #sum_P = sum(P[i:i+K])
    if now_sum > max_sum:
        max_sum = now_sum
        max_index = i

#print(max_sum)
#print(max_index)

# 隣接したK個のリスト
kk = P[max_index:max_index+K]

# kの期待値を計算
max_kk = max(kk)
dp = [0]
for i in range(1, max_kk+1):
    dp.append(dp[i-1] + i)
#print(dp)

ans = 0
for k in kk:
    ans += dp[k]/k

print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
# -*- coding: utf-8 -*-

[N, K] = [int(i) for i in input().split()]
P = [int(i) for i in input().split()]

sum_list = []
for i in range(len(P)-(K-1)):
    sum_list.append(sum(P[i: i+K]))

#print(sum_list)
max_index = sum_list.index(max(sum_list))
#print(max_index)

# 隣接したK個のリスト
kk = P[max_index: max_index+K]

# kの期待値を計算
max_kk = max(kk)
dp = [0]
for i in range(1, max_kk+1):
    dp.append(dp[i-1] + i)
#print(dp)

ans = 0
for k in kk:
    ans += dp[k]/k

print(ans)

Fixed submission:
# -*- coding: utf-8 -*-

#def f(x):
#    if x == 1:
#        return 1
#    else:
#        return f(x-1) + x

[N, K] = [int(i) for i in input().split()]
P = [int(i) for i in input().split()]

max_index = 0
now_sum = sum(P[:K])
max_sum = now_sum
for i in range(1, len(P)-(K-1)):
    now_sum -= P[i-1]
    now_sum += P[i+K-1]
    #sum_P = sum(P[i:i+K])
    if now_sum > max_sum:
        max_sum = now_sum
        max_index = i

#print(max_sum)
#print(max_index)

# 隣接したK個のリスト
kk = P[max_index:max_index+K]

# kの期待値を計算
max_kk = max(kk)
dp = [0]
for i in range(1, max_kk+1):
    dp.append(dp[i-1] + i)
#print(dp)

ans = 0
for k in kk:
    ans += dp[k]/k

print(ans)