about codekata problem

in codekata even i am writing a correct code it fails every time why this happens?please help Test case is failed every time.

print("Enter 'x' for exit.");

rad = input("Enter radius of circle: ");

if rad == 'x':

exit();

else:

radius = float(rad);

circumference = 23.14radius;

print("\nCircumference of Circle =",circumference);