current_users=['NiuNiu','GuRR','LOLO']
new_users=['GurR','Niu Ke Le','LoLo','Tuo Rui Chi' ]
list1=[]
for i in current_users:
    list1.append(i.lower())
list2=[]
for i in new_users:
    list2.append(i.lower())
for x in new_users:
    if x.lower() in list1:
        print(f"The user name {x} has already been registered! Please change it and try again!")
    else:
        print(f"Congratulations, the user name {x} is available!")