type muchie = ^nod;
     nod = record n:longint; a:muchie; end;

var v:array [0..100000] of muchie;
    par:array [1..100000] of longint;
    sol, temp:array[-1..600000] of longint;
    m, n, i, x, y, vf, t, c:longint;
    p, r, q, qq:muchie;
    f, g:text;
    k:boolean;
    buf1, buf2:array[1.. 1 shl 17] of char;

begin
assign (f, 'ciclueuler.in'); settextbuf (f, buf1); reset (f);
assign (g, 'ciclueuler.out'); settextbuf (g, buf2); rewrite (g);

readln (f, n, m);
for i := 1 to m do
  begin
  readln (f, x, y);
  if v[x]= nil then
    begin
    new(v[x]); v[x]^.a:=nil; v[x]^.n:=y;
    end
               else
    begin
    p:=v[x];
    while p^.a <> nil do p:=p^.a;
    new(r); p^.a:=r; r^.a:=nil; r^.n:=y;
    end;

  if v[y]= nil then
    begin
    new(v[y]); v[y]^.a:=nil; v[y]^.n:=x;
    end
               else
    begin
    p:=v[y];
    while p^.a <> nil do p:=p^.a;
    new(r); p^.a:=r; r^.a:=nil; r^.n:=x;
    end;
  inc(par[x]); inc(par[y]);
  end;


c:=1;
for i := 1 to n do
  begin
  if par[i] mod 2 = 1 then c:=-1;
  end;

i:=0;
if c=-1 then writeln (g, c)
            else
  begin
  p:=v[c]; qq:=p;
  vf:=1; t:=0;
  while vf>0 do
    begin
    if p <> nil then
      begin
      temp[vf]:=p^.n;
      inc (vf);
      if p = qq  then v[c]:=v[c]^.a
                 else qq^.a:=p^.a;
      q:=v[p^.n]; qq:=q;
      q:=v[p^.n]; qq:=q;
      k:= true;
      while k and (q<> nil) do
        begin
        if q^.n=c then
          begin
          k := false;
          if qq=q then v[p^.n]:=v[p^.n]^.a
                  else qq^.a:=q^.a;
          end;
        q:=q^.a; if qq^.a <> q then qq:=qq^.a;
        end;
      c:=p^.n;
      p:=v[p^.n]; qq:=p;
      end
                else
      begin
      inc (t);
      dec(vf);
      sol[t]:= temp[vf];
      p:=v[temp[vf-1]]; qq:=p;
      c:=temp[vf-1];
      end;
    end;
  end;

for i := 1 to t-1 do write (g, sol[i], ' ');

close (f); close (g);
end.