Appy and Balloons

Appy loves balloons! She wants you to give her balloons on each of $N$ consecutive days (numbered $1$ through $N$); let's denote the number of balloons Appy wants on day $i$ by $A_i$. The problem is that you only have $M$ balloons. Fortunately, you can give her candies instead of balloons as well. On each day $i$, Appy accepts $B_i$ candies per each balloon you do not give her — formally, if you g