渐变的圆

import turtle
number = int(input())
turtle.screensize(600,500,'white')
turtle.pensize(3)
turtle.pencolor('blue')
turtle.fillcolor('yellow')
turtle.begin_fill()
for i in range(3,number):
    turtle.circle(50, steps=i)
    turtle.forward(100)
turtle.circle(50, steps=number)
if number == 1
   turtle.circle(50)
else:
    turtle.forward(100)
    turtle.circle(50)
turtle.end_fill()
turtle.hideturtle()
turtle.done()