$$539-142$$ divided by $$4$$ has a remainder of~\uline{~~~~~~~~~~}~． 
Overseas Competition->Knowledge Point->Number Theory Modules->Remainder Problems->Characteristics of Remainder 
$$539\div 4$$ R $$3$$；$$142\div 4$$ R $$2$$；$$539-142$$ divided by $$4$$, the remainder is 3-2=1. 