Please tell me, how I must use M from input???

And, by the way, why second person from sample input will poison?

Assume the first man eats no products.

In canteen you can find only M products,
so if for us are bad only N - M products we have chance
to live and if for us are bad N - M + 1 products
(we know that one of them exactly is poisoned) we will die.

Thanks for your hint, got AC... :)

Does each student eat M products from canteen?
if so, do we have after  i-st student N-M*i products?
And last student can't get 3 products.

Otherwise, why second student don't take "Rafinat+Pastila+Chocolate" and stay alive?

> Does each student eat M products from canteen ?
yup
> do we have after i-st student N-M*i products ?
no, each student receive same products
menu is fixed and it consist of M products from N given
from the example first student test the food and he is OK, that means there are no stuffs in menu from his dangerous list { Rafinad, Kefir, Imbir }
so here the menu consist of 3 stuffs from { Pastila, Smetana, Chokolade, Kljukva }
the second student have 2 dangerous products from leaved and in any combination of menu he die :/

let products which eat first student will be in list A
all other products in list B
for each student we count products, which his take, which in list B
if this counter = 0
then we write YES
if this counter <= N - X - M, where X is count of products in list A
then we write MAYBE
else we write NO