If $\int \frac{\left(\sqrt{1+x^2}+x\right)^{10}}{\left(\sqrt{1+x^2}-x\right)^9} \mathrm{~d} x=\frac{1}{\mathrm{~m}}\left(\left(\sqrt{1+x^2}+x\right)^0\left(\pi \sqrt{1+x^2}-x\right)\right)+\mathrm{C}$ where C is the constant of integration and $m, n \in \mathbf{N}$, then $m+n$ is equal to $\_\_\_\_$ .