Andy is always a hungry man. He never stopped eating something sweet, expecially cakes.
Yesterday his mother gave him some pocket money, and now, he has M dollars all together.
The cake shop provides N pieces of cakes, and each of them costs ai dollars respectively.
Fortunately, Andy has K discount coupons for that cake shop. When we use a coupon, we can buy a cake at a lower prize of bi dollars instead of the original ai dollars.