const
    maxN=100002;
    maxE=500002;
type ed=record
     x,y:longint;
     end;
var raspuns,st:array[1..MaxE] of longint;
    edges,nodes,i,j,u,k:longint;
    edge:array[1..MaxE] of ed;
    degree:array[1..MaxN] of longint;
function eulerian:boolean;
begin
    i:=1;
    while (i<=nodes) and not(odd(degree[i])) and (degree[i]<>0) do inc(i);
    if i>nodes then eulerian:=true
    else eulerian:=false;
end;


function next(x:integer):integer;
var i,j:integer;
begin
     for i:=1 to edges do
     if edge[i].x=x then
     begin
          next:=edge[i].y;
          exit;
     end;

     for i:=1 to edges do
     if edge[i].y=x then
     begin
          next:=edge[i].x;
          exit;
     end;


end;


procedure erase(a,b:integer);
var i,j:integer;
begin
     for i:=1 to edges do
     if (edge[i].x=a) and (edge[i].y=b) then
     begin
          edge[i].x:=0;
          edge[i].y:=0;
          break;
     end;
     for j:=i to edges do
     begin
          edge[j].x:=edge[j+1].x;
          edge[j].y:=edge[j+1].y;
     end;
     dec(edges);
     fillchar(degree,sizeof(degree),0);
     for i:=1 to nodes do
    begin
        for j:=1 to edges do
        if (edge[j].x=i) or (edge[j].y=i) then inc(degree[i]);
    end;
end;

procedure push_st(node:longint);
begin
    inc(u);
    st[u]:=node;
end;

procedure pop;
begin
   st[u]:=0;
   dec(u);
end;

//Cautare ciclu eulerian
procedure Euler(node:longint);
var w,neigh:longint;
begin
    push_st(node);
    while u>0 do
    begin
        node:=st[u];
        if degree[node]=0 then
        begin
           inc(k);
           raspuns[k]:=node;
           pop;
        end
         else
         begin
              neigh:=next(node);
              erase(node,neigh);
              push_st(neigh);
         end;
    end;

end;


{procedure eulerfind(node:longint);
var neigh:longint;
begin
     while degree[node]>0 do
     begin
         neigh:=next(node);
         erase(node,neigh);
         eulerfind(neigh);
     end;
     inc(u);
     raspuns[u]:=node;
end; }

Begin
     assign(input,'ciclueuler.in'); reset(input);
     assign(output,'ciclueuler.out'); rewrite(output);
     fillchar(degree,sizeof(degree),0);
     readln(input,nodes,edges);
     for i:=1 to edges do
     begin
        readln(input,edge[i].x,edge[i].y);
        if edge[i].x<>edge[i].y then begin inc(degree[edge[i].x]); inc(degree[edge[i].y]); end;
     end;
     //verificare
      if not(eulerian) then
      begin
          write('-1');
          exit;
      end;
     //verificare
     u:=0; k:=0;
     Euler(1);
     //EulerFind(1);
     for i:=2 to k do write(output,raspuns[i],' ');
     close(input);
     close(output);
End.