Question 4
Two people, $A$ and $B$, go up a staircase with a certain number of steps. $A$ goes up 2 steps in one stride, while $B$ goes up 5 steps in one stride, except if $A$ finds only 1 step before the last stride, then he will go up just 1 step to finish, and if $B$ finds 4 or less steps remaining before the last stride, then $B$ will go up whatever steps remaining to climb to finish. $B$ took 6 strides less than $A$ to finish climbing this staircase. Determine all possible numbers of steps for this staircase can have.