var s:string;

i,j,k:integer;

Unique:boolean;

BEGIN

  for i := 1000 to 9999 do

  begin

     s := str(i);

     Unique:=true;

     for j: = 1 to length(s)-1 do

        for k := j+1 to length(s) do

        begin

           if s[j] = s[k] then Unique:=false;

        end;

     if Unique then

       writeln(i);

  end;

END.

может длинее, но универсальное.

Verified answer

var
a: integer;
c1, c2, c3, c4: integer;

begin
for a := 1000 to 9999 do
begin
c1 := a div 1000;
c2 := (a div 100) mod 10;
c3 := (a div 10) mod 10;
c4 := a mod 10;
if (c1 <> c2) and (c1 <> c3) and (c1 <> c4) and (c2 <> c3) and (c2 <> c4) and (c3 <> c4)
then writeln(a);
end;
end.