Seven students, $$A$$, $$B$$, $$C$$, $$D$$, $$E$$, $$F$$ and $$G$$ are playing a chess match. So far, $$A$$ has played $$4$$ matches, $$B$$ has played $$6$$ matches, $$C$$ has played $$2$$ matches, $$D$$ has played $$1$$ matches, $$E$$ has played $$3$$ matches and $$G$$ has played $$5$$ matches. At this point, $$F$$ has played~\uline{~~~~~~~~~~}~matches. 
Overseas Competition->Knowledge Point->Counting Modules->Inclusion-Exclusion Principle