In Python2, input is evaluated, input() is equivalent to eval(raw_input()). When you enter klj, Python tries to evaluate that name and raises an error because that name is not defined.
Use raw_input to get a string from the user in Python2.
Demo 1: klj is not defined:
>>> input()
klj
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<string>", line 1, in <module>
NameError: name 'klj' is not defined
Demo 2: klj is defined:
>>> klj = 'hi'
>>> input()
klj
'hi'
Demo 3: getting a string with raw_input:
>>> raw_input()
klj
'klj'