Program ming;
Var
i,n,k,f:integer;
a:array[1..1000] of 0..1;
begin
readln(k);
for i:=1 to k do begin
read(n);
if a[n]=0 then f:=f+1;
a[n]:=1; end;
writeln(f);
for i:=1 to 1000 do begin
if a[i]=1 then begin
write(i);
if i<>f then write( );
end;
end;
End.