for(<>){
$i=1;@m=();
while(/\S /||$i--){
s/^(\d\S*) (\d\S*)/"$1$2".(pop@m)/e and s/^/(pop@m)." "/e and redo;
s/(\S+) // and push@m,$1;
}s/./$& /g;s/^ +| $//g;
print
}