How would you prove that for $\displaystyle 1\leq p<s<\infty$

$\displaystyle L^{p}(\mathbb{N},\cal{S},\mu) \subseteq$ $\displaystyle L^{s}(\mathbb{N},\cal{S},\mu)$

where $\displaystyle \cal{S}$ is a sigma algebra of $\displaystyle \mathbb{N}$ and $\displaystyle \mu$ is a counting measure.