For any two points $M$ and $N$ in the X Y -plane, let $\overrightarrow{M N}$ denote the vector from $M$ to $N$, and $\overrightarrow{0}$ denote the zero vector. Let $\mathrm{P}, \mathrm{Q}$ and $R$ be three distinct points in the XYplane. Let S be a point inside the triangle $\triangle P Q R$ such that $$ \overrightarrow{S P}+5 \overrightarrow{S Q}+6 \overrightarrow{S R}=\overrightarrow{0} $$ Let $E$ and $F$ be the mid-points of the sides PR and QR , respectively. Then the value of $\frac{\text { length of the line segment } E F}{\text { length of the line segment } E S}$ is $\_\_\_\_$ .