long-number arithmetic?
i thank that the resulting number is the next summ:
  N
 ___ i        i
 \_ C   *(K-1)
 /__ N-i

i=[N/2],   where C is  i!/((N-i)!*(2*i-N)!)

and so we have to apply a long-number arithmetic,am I right?
but it is no so fast for this problem!i get a time limit exceeded
(it was worked for #1012)
help me please
maybe there are another faster algorithm?

> long-number arithmetic?
> i thank that the resulting number is the next summ:
>   N
>  ___ i        i
>  \_ C   *(K-1)
>  /__ N-i
>
> i=[N/2],   where C is  i!/((N-i)!*(2*i-N)!)
>
> and so we have to apply a long-number arithmetic,am I right?
> but it is no so fast for this problem!i get a time limit exceeded
> (it was worked for #1012)
> help me please
> maybe there are another faster algorithm?