## algebraic geometry

"F) Finally, we may define $Pic(X)$ to be the group $Div(X)/$(pinc. divisors). Then $R_X$ itself is a UFD if and only if $Pic(X)=(0)$."

This part is the 6th line from the top on the page 19 of "Algebraic geometry 1:Complex Projective Varieties(by David Mumford)"

Can you prove this?