var i,n,a,b,m:longint;
    vv:array[1..100000] of 0..1;
    v:array[1..1000,1..1000] of 0..1;
    ok:boolean;
procedure euler(nod:longint);
   begin
     for i:=1 to n do
         if v[nod,i]=1 then
           begin
             v[nod,i]:=0; v[i,nod]:=0;
             euler(i);
           end;
write(nod,' ');
   end;
begin
assign(input,'ciclueuler.in'); reset(input);
assign(output,'ciclueuler.out'); rewrite(output);
readln(n,m);
for i:=1 to m do
   begin
     readln(a,b);
     v[a,b]:=1; inc(vv[a]); inc(vv[b]);
     v[b,a]:=1;
   end;
   ok:=true;
for i:=1 to n do if vv[i] mod 2=1 then ok:=false;
if ok then
        begin
         euler(a);
        end
      else writeln('-1');
close(output);
close(input);
end.