Here is a sequence as follows:  $$2$$~ $$3$$~ $$1$$ $$4$$ ~$$2$$~ $$3$$~ $$1$$ $$4$$ ~$$2$$~ $$3$$~ $$1 $$ $$4$$ $$\cdots \cdots $$  What\textquotesingle s the $$100$$th number? 
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