Suppose $A_1,A_2\mathrm{.......}{A}_{30}$  are thirty sets each with five elements and $B_1,B_2\mathrm{........}{B}_n$  are n sets each with three elements such that ${\displaystyle \underset{i=1}{\overset{30}{\cup }}{A}_i={\displaystyle \underset{i=1}{\overset{n}{\cup }}{B}_i}}=S$ . If each element of $S$  belongs to exactly ten of the $A_i\text{'}\text{s}$ and exactly 9 of the $B_i\text{'}\text{s}$  then $n$  is divisible by