Use $\sum 2^{-n}(\|x-y\|_n \wedge 1)$ for the distance on $X$ Y$and $\sum $\sum 2^{-n}(\|x-y\|_n \wedge 2)$ for the distance on $Y$. X$. 1 Use$\sum 2^{-n}(\|x-y\|_n \wedge 1)$for the distance on$X$and $\sum 2^{-n}(\|x-y\|_n \wedge 2)$for the distance on$Y\$.