program Project1;
{$APPTYPE CONSOLE}
uses
SysUtils;
var
  arr:array[1..40] of integer;
  n,i,s:integer;
begin
  //reset(input,'danger.in');
  //rewrite(output,'danger.out');
  read(n);
  arr[1]:=0;
  s:=3;
  for i:=2 to n do
    begin
      s:=s*3;
      arr[i]:=arr[i-1]+i-1;
    end;
  write(s-arr[n]);
  readln;
  readln;
end.