($n,$m,$s,$g)=<>=~/\d+/g;
for(<>){
    ($a,$b,$c)=/\d+/g;
    $c{$a,$b}=$c{$b,$a}=$c;
}
$v[$g]=1;
push@a,$g;
while(@a){
    $a=pop@a;
    for$b(0..$n-1){
	if($c=$c{$a,$b}){
	    if($v[$b]==0||$v[$b]>$v[$a]+$c) {
		$v[$b]=$v[$a]+$c;
		$p[$b]=$a;
		push@a,$b;
	    }elsif($v[$b]==$v[$a]+$c) {
		$p[$b].=" $a";
		push@a,$b;
	    }
	}
    }
}
print $s;
$a=$s;
do{
    ($a)=sort{$a-$b}$p[$a]=~/\d+/g;
    print" $a";
}while($a!=$g);