var i:longint;

function car(k:longint):char;
begin
car:=chr(k+ord('a'));
end;

begin
for i:=0 to 333332 do
 begin
 write(car((i div 676) mod 26),car((i div 26) mod 26),car(i mod 26));
 end;
write('a');
end.

I got AC 0.078 25 Kb
var
    i:longint;
begin
    for i:=1 to 333333 do
    write(chr(97+((i div 676) mod 26)),chr(97+((i div 26) mod 26)),chr(97+(i mod 26)));
    write('a');
end.

Thank you,it's really amazing!!!!!!!!!!

me too.

forn(26) fornj(26) fornk(26)
    {
        if (i == j && j==k) continue;
        if (M[i][j][k]) continue;


        M[i][j][k]=true;
        M[k][i][j]=true;
        M[j][k][i]=true;
        //and stuff here;
    }
}