# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")

def solution(A):
    # write your code in Python 3.6
    preSum = [0] * len(A)
    for i in range(len(A)):
        preSum[i] = preSum[i-1] + A[i]
    Min, MinI = preSum[1] / 2, 0
    for i in range(2, len(preSum)):
        cur = (preSum[i] - preSum[i-2]) / 2
        if Min > cur:
            Min, MinI = cur, i - 1
    if len(A) <= 2:
        return MinI
    cur = preSum[2] / 3
    if Min > cur:
        Min, MinI = cur, 0
    for i in range(3, len(preSum)):
        cur = (preSum[i] - preSum[i-3]) / 3
        if Min > cur:
            Min, MinI = cur, i - 2
    return MinI