main::IO()
main =do
  n<-fmap read getLine
  let kaijou 0  =1
      kaijou n  = n * kaijou (n-1)
      nCr n r =kaijou n `div` (kaijou r) `div` (kaijou (n-r))

      joutai n =[(x,y)|x<-[0..n],y<-[0..n] ,x+2*y==n]

  print .sum . map (\(x,y)->nCr (x+y) x) $joutai n