from turtle import *
x=100
color("white")
goto(-1/2*x,-1/2*x)
color("black")
for i in range (4):
    for i in range (6):
        forward(20)
        right(90)
        forward(20)
        left(90)
        forward(20)
        left(90)
        forward(20)
        right(90)
    left(90)
mainloop()