#!/usr/bin/perl -l print$_=pop;while(s/(.)(?=(.))/$1+$2-9*($1+$2>9)/eg){s/.$//;print}
#!/usr/bin/perl -l $_=pop;a:print;if(s/(.)(?=(.))/$1+$2-9*($1+$2>9)/eg){s/.$//;goto a}