program p1156;

type  re=record
          t:integer;
          s:set of byte;
        end;
var a:array[1..100,0..1]of re;
    b:array[1..100]of byte;
    xs:array[1..100]of set of byte;
    m,n,i,j,k,x,y,t:integer;
    s:set of byte;
    f:boolean;

procedure inpu;
var i:integer;
begin
  readln(n,m);
  for i:=1 to m do begin
    readln(x,y);
    xs[x]:=xs[x]+[y];
    xs[y]:=xs[y]+[x];
  end;
end;

procedure pret;
var i,j:integer;
    f:boolean;
begin
  k:=0;
  s:=[1..2*n];
  while s<>[] do begin
    inc(k);
    for i:=1 to 2*n do
      if i in s then break;
    inc(a[k,0].t);
    a[k,0].s:=a[k,0].s+[i];
    s:=s-[i];
    f:=true;
    j:=0;
    while f do begin
      j:=1-j;
      f:=false;
      for i:=1 to 2*n do
        if i in s then
          if xs[i]*a[k,1-j].s<>[] then begin
            inc(a[k,j].t);
            a[k,j].s:=a[k,j].s+[i];
            s:=s-[i];
            f:=true;
          end;
    end;
  end;
end;

procedure outpu;
var i:integer;
begin
  for i:=1 to 2*n do
    if i in s then write(i,' ');
  writeln;
  for i:=1 to 2*n do
    if not(i in s) then write(i,' ');
  writeln;
  halt;
end;

procedure try(i:integer);
var j:integer;
begin
  for j:=0 to 1 do begin
    inc(t,a[i,j].t);
    s:=s+a[i,j].s;
    b[i]:=j;
    if i<k then begin
      if t<n then try(i+1)
    end
    else
      if t=n then outpu;
    s:=s-a[i,j].s;
    dec(t,a[i,j].t);
  end;
end;

begin
  inpu;
  pret;
  t:=0;
  try(1);
  writeln('IMPOSSIBLE');
end.