sub stest
{
    my $str = shift;
    my $last_index=1;
    my @sorted_indexes = sort { $a <=> $b } @_;
    die "bad index" if( $sorted_indexes[0] < 1 );
    
    my $offset;
    do {
	$last_index += ( 
	    ( $offset = 
	        ( (shift @sorted_indexes 
		   || return true) 
		  - $last_index
		) || next 
	    )
	);
	substr($str, 0, $offset, "");
    } while( $str=~/^01|^10/ );
    return false;
}