4. Point $K$ lies on side $B C$ of parallelogram $A B C D$, and point $M$ lies on its side $A D$. Segments $C M$ and $D K$ intersect at point $L$, and segments $A K$ and $B M$ intersect at point $N$. Find the maximum value of the ratio of the areas of quadrilaterals $K L M N$ and $A B C D$.