from typing import List


def cums(counts: List[int]) -> List[int]:
    """Turn a list of counts into a cumulative list.

    :param list[int] counts: the list of counts
    :returns: cumulative counts, e.g., [1,2,3] -> [1,3,6]
    :rtype: list[int]
    """
    accumulator = 0
    running_sums = []
    for count in counts:
        accumulator += count
        running_sums.append(accumulator)
    return running_sums