var
n,i,j:integer;
a:array[1..1000] of boolean;
begin
assign(input,'random.in');
assign(output,'random.out');
reset(input);
rewrite(output);
fillchar(a,sizeof(a),false);
read(n);
for i:=1 to n do
begin
read(j);
a[j]:=true;
end;
j:=0;
for i:=1 to 1000 do
if a[i] then j:=j+1;
writeln(j);
for i:=1 to 1000 do
if a[i] then write(i,' ');
close(input);
close(output);
end.