# Factorial!

If the expression $$\frac{3}{1!+2!+3!}$$ + $$\frac{4}{2!+3!+4!}$$ + ...... + $$\frac{2001}{1999!+2000!+2001!}$$

Can be written as $$\frac{1}{a!}$$ - $$\frac{1}{b!}$$, Find a+b.

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