Reaper Reaps

*I have no compassion, I only exist to collect the souls of the living.* On Halloween, Grim Reaper wants to reap souls from houses. There are $N$ houses. The $i$-th of them has a *safety level* of $A_i$ and has $B_i$ people living in it. The Reaper has an ability level, denoted $L$. Initially, $L = 0$. When the Reaper visits a house, the following two things happen in order: - If $L \geq A_i