Completeness of continuous real valued functions with compact support

How can I show that the space of continuous real valued functions on R with compact
support in the usual sup norm metric is not complete ?
I know that this result can be proved by using the fact that the given space is dense in the space of all continuous functions that vanish at infinity which is complete ,
but I want a bit easier proof of this as I have not studied measure theory . I was
trying to solve it directly from the definition of completeness.

Thanks for any help.

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