program acm1095;
var a:array[0..20] of int64;
    i,j,n:longint;
begin
  a[0]:=1; a[1]:=1;
  for i:=2 to 20 do
    for j:=i-1 downto 0 do
     a[i]:=a[i]+a[i-1-j]*a[j];
  while not eof do
   begin
     readln(n);
     writeln(a[n]);
   end;
end.
     
/**************************************************************
	Problem: 2120
	User: admin
	Language: Pascal
	Result: Wrong Answer
****************************************************************/