Project Euler #1 Python Using list sum and while loops :     x = 3
    y = 5
    x_list = []
    y_list = []

    while x < 1000:
        x_list.append(x)
        x += 3
   
    while y < 1000:
        y_list.append(y)
        y += 5

    numsum = sum(x_list + y_list)
    print(numsum)

I am getting an output of 266333, and am unsure of why this code doesn't get me the correct answer