def cumulsum(ls):
    updated_list = []
    counter = 0

    while counter < len(ls):
        thing_to_add = 0
        if(counter == 0):
            thing_to_add += ls[0]
        else:
            for index in range(0,counter+1):
                thing_to_add += ls[index]
        updated_list.append(thing_to_add)
        counter = counter + 1
    return updated_list