my $cnr = 0;
while ($cnr < 1) {
    my $xda = int rand (0 .. $total);
    if ( $aob[$xda][ $y - 1 ] ne q{}) {
        $aob[$x][$y] = $z + $aob[$xda][ $y - 1 ];
        $cnr++;
    }
}