current_users=['Niuniu','Niumei','GURR','LOLO'] new_users=['GurR','Niu Ke Le','LoLo','Tuo Rui Chi'] s1=list(map(str.lower,current_users)) s2=list(map(str.lower,new_users)) for i in [0,1,2,3]: a=s2[i] if a in s1: print('The user name {} has already been registered! Please change it and try again!'.fo...