Let $p$ be the number of all triangles that can be formed by joining the vertices of a regular polygon P of n sides and q be the number of all quadrilaterals that can be formed by joining the vertices of P. If $\mathrm{p}+\mathrm{q}=126$, then the eccentricity of the ellipse $\frac{x^2}{16}+\frac{y^2}{\mathrm{n}}=1$ is: