var d: array [1..1000000] of integer;
    a, a2, p, ans: array [1..5000] of array of integer;
    mark: array[1..1000000] of boolean;
    i,n,s,min,j,q,f, x, y, z, t, len, m: integer;




begin

//reset(input, 'dijkstra.in'); rewrite(output, 'dijkstra.out');
read(n,m,s,f);


for i:=1 to m do begin
  read(x, y, z);
  setlength(a[x], length(a[x] + 1));
  setlength(a[y], length(a[y] + 1));
  setlength(a2[x], length(a2[x] + 1));
  setlength(a2[y], length(a2[y] + 1));
  a[x][length(a[x])] := y;
  a[y][length(a[y])] := x;
  a2[x][length(a2[x])] := z;
  a2[y][length(a2[x])] := z;
end;
d[s]:=0;

for i:=1 to n do begin
  if (i<>s) then d[i]:=1000000000;
  mark[i]:=False;
end;

for i:=1 to n do begin
d[n+1]:=1000000001;
  min:=n+1;
    for j:= 1 to n do begin
      if (d[min]>d[j]) and (mark[j]=False) then min:=j;
    if d[min] =1000000000 then break;
    if d[min] <> 1000000000 then begin
      mark[min]:=True;
      for j:=1 to length(a[min]) do begin
        t := a[min][j];
        len := a2[min][j];
        if(d[min]+ len < d[t]) then begin
          d[t] := d[min]+len;
          p[t] := min;
      end;
    end;
end;
end;
end;
  if (d[f]=1000000000) then writeln(-1)
  else begin
    writeln(d[f]);
    x:= f;
    for i:= 1 to d[f] do begin
      ans[i] := x;
      x := p[x];
    end;
    for i:= d[f] downto 1 do
       writeln(ans[i], ' ');
  end;
  readln;
  readln;
 //close(input); close(output);

end.