$/=a;@a=<>=~/\d+/g; ($z)=grep{!$a[$_]}0..15; while($z<15){ if($z>3 && $a[$z-4]==$z+1){ $a[$z]=$z+1; $z-=4; }elsif($z<12 && $a[$z+4]==$z+1){ $a[$z]=$z+1; $z+=4; }elsif($z%4 && $a[$z-1]==$z+1){ $a[$z]=$z+1; $z--; }elsif($z%4<3 && $a[$z+1]==$z+1){ $a[$z]=$z+1; $z++; }else{ last; } } $a[$z]=16; print grep($a[$_]-$_-1,0..15)?No:Yes