Program Chernobyl_eagles;
 var
   a:array[0..1000] of integer;
   n,i,k,v:integer;

Begin
  fillchar(a,sizeof(a),0);
  read(n); a[0]:=1;
  if n=1 then begin writeln(1); halt; end;
  if n=2 then begin writeln(2); halt; end;
  if n=3 then begin writeln(3); halt; end;

  if n mod 3=0 then begin n:=n-3; a[1]:=3; end;
  if n mod 3=1 then begin n:=n-4; a[1]:=4; end;
  if n mod 3=2 then begin n:=n-2; a[1]:=2; end;

  k:=n div 3;
  for v:=1 to k do
   begin
     for i:=1 to a[0] do a[i]:=a[i]*3;
     for i:=1 to a[0] do if a[i]>9 then
      begin a[i+1]:=a[i+1]+a[i] div 10; a[i]:=a[i] mod 10; end;
     if a[i+1]>0 then a[0]:=i+1;
   end;
  for i:=a[0] downto 1 do write(chr(ord(a[i])+48)); writeln;
End.

Tip 1:

  if n=1 then begin writeln(1); halt; end;
  if n=2 then begin writeln(2); halt; end;
  if n=3 then begin writeln(3); halt; end;

is equal to

  if (n > 0) and (n < 4) then
  begin
    WriteLn(n);
    exit
  end;

Tip 2:

  write(chr(ord(a[i])+48));

is equal to

  write(a[i]);

Tip 3:

  I think that there is a test with input "0" and output "1".
  Don't ask me why, I don't know.