Please what's the problem with my code

Question

i want to raise an exception when the user does not type the first word as 'k'or'K'

print("enter name\n")
a=input("name:")

if a[0]!="k" or a[0]!="K":
raise ValueError("invalid name")

else:
print(a)

but this code isn't working, it always raises an error. Please help!