暴力模拟无算法

Program P1868;
Var
   c:char;
   n,i,j,k:longint;
   a:array[0..10000] of longint;
function is_ant:boolean;
var
   i,j,k:longint;
begin
   for k:=1 to n shr 2 do
      for i:=1 to n-k shl 1-1 do
         if ((a[i]<a[i+k]) and (a[i+k]<a[i+2*k])) or ((a[i]>a[i+k]) and (a[i+k]>a[i+2*k])) then exit(false);




   exit(true);
end;
Begin
   while true do
   begin
      read(c);
      if c='0' then break;
      val(c,n);
      repeat
         read(c);
         if c=':' then break;
         n:=n*10+ord(c)-48;
      until false;
      for i:=1 to n do
      begin
         read(j);
         a[j]:=i;
      end;

      if is_ant then writeln('yes') else writeln('no');

      readln;

   end;
end.