using input() to control python turtles

[amh80]

I wrote the code below to try to get the turtle below to move the amount input, but I cannot seem to figure out why defining c will not work. How can I get the input to work? I keep getting an error message "ExternalError: TypeError: Cannot read property 'instance' of undefined on line 13." Line 13 is turtle.forward(int©).

import turtle
myTurtle = turtle.Turtle()
myTurtle.forward(100)
myTurtle.right(90)
myTurtle.penup()
myTurtle.forward(100)
myTurtle.right(90)
myTurtle.pendown()
myTurtle.pencolor("green")
myTurtle.right(90)
myTurtle.forward(100)
c=input(int())
turtle.forward(int(c))
myTurtle.back(100)