同心圆

import turtle
r=eval(input("半径："))
x=eval(input("个数："))
c=input("颜色：")
turtle.pencolor(c)
turtle.pensize(3)
for i in range(x):
    turtle.circle(r)
    turtle.up()
    turtle.right(90)
    turtle.forward(20)
    turtle.left(90)
    turtle.down()
    r += 20