It seems to me it is simple. Every count from 1 to 3000 is a sequence
3*3*3*...*2 or 3*3*3*...*3 or 3*3*3*...*4. Just long number
ariphmetics.
But Wrong Answer! Maybe my output is incorrect? Help me! Here is the
text of my program:

program DY_1222;
const
   ML=1000;
type
   TArray = array [1..ML] of integer;
var
   n,i1: longint;
   r: TArray;

{returns number of first non-zero position}
function GetStart(op: TArray): longint;
var
   prm: longint;
begin
   prm:=1;
   while op[prm]=0 do inc(prm);
   GetStart:=prm;
end;

{multiplies current array on 3}
procedure P(var op: TArray);
var
   prm: longint;
   mem: integer;
   buf: TArray;
begin
   mem:=0;
   FillChar(buf,SizeOf(buf),0);
   for prm:=ML downto GetStart(op) do
      begin
         buf[prm]:=(op[prm]*3+mem) mod 10;
         mem:=(op[prm]*3+mem) div 10;
      end;
   buf[prm-1]:=mem;
   op:=buf;
end;

begin
   Readln(n);
   if n>4 then
      begin
         r[ML]:=n-((n-2) div 3)*3;
         if r[ML]=0 then r[ML]:=1;
         for i1:=1 to (n-2) div 3 do P(r);
         for i1:=GetStart(r) to ML do Write(r[i1]);
      end
         else Write(n);
end.

IMHO the ACM'system of checking is wrong. When I output my answer
as ...Write(r[i])...Write(r[i])... I receive WA, but when I output
may answer as ...Write(chr(ord(r[i])+48))...Write(chr(ord(r[i])
+48))... I receive AC. My problems with 1206 were the same. Admins,
check!