var i,n,m,tam: longint;
a,b: array[1..1000000] of longint;
begin
	read(n,m);
	for i:=1 to n do a[i]:=1;
	for i:=1 to m do  read(b[i]);
	for i:=m downto 1 do
	begin
		tam:=b[i];
		if a[tam]=1 then 
			begin 
				write(tam,' '); 
				dec(a[tam]); 
			end;
	end;

for i:=1 to n do
	if a[i]=1 then
	begin
		write(i,' ');
		dec(a[i]);
	end;
end.