### maxSumOfThreeSubarrays 
from typing import *
def f_gold(nums: List[int], k: int) -> List[int]:
    s = s1 = s2 = s3 = 0
    mx1 = mx12 = 0
    idx1, idx12 = 0, ()
    ans = []
    for i in range(k * 2, len(nums)):
        s1 += nums[i - k * 2]
        s2 += nums[i - k]
        s3 += nums[i]
        if i >= k * 3 - 1:
            if s1 > mx1:
                mx1 = s1
                idx1 = i - k * 3 + 1
            if mx1 + s2 > mx12:
                mx12 = mx1 + s2
                idx12 = (idx1, i - k * 2 + 1)
            if mx12 + s3 > s:
                s = mx12 + s3
                ans = [*idx12, i - k + 1]
            s1 -= nums[i - k * 3 + 1]
            s2 -= nums[i - k * 2 + 1]
            s3 -= nums[i - k + 1]
    return ans