Sliding Window Technique (Fixed-Size Window)

arr = list(map(int,input().split()))
#prefix = []
#c = 0
#for x in arr:
    # c+=x
    #print(*prefix)
#def sum_range(L,R):
    #if L == 0:
       # return prefix[R]
    #else:
       # return prefix[R] - prefix[L-1]
#print(sum_range(1,3))

k = 3
sum_array = sum(arr[:k])
#print(sum_array)
max_array = sum_array
for x in range(k,len(arr)):
    sum_array = sum_array - arr[x-k] + arr[x]
    max_array = max(max_array,sum_array)
print(max_array)