<style type="text/css" media="screen">
div {
border: 1px solid red;
width: 45%;
height: auto;
}

.left {
    float: left;
    clear: left;

}

.right {
    float: right;
    clear: right;
}

</style>
<?php

$c = array('111<br>1111111 <br>1111','222 222 <br>22','4444 444<br>44<br>4444 <br>44 ');

for ($index = 0; $index < 20; $index++) {
        echo '<div class="'.($index%2 === 0 ? 'left':'right').'">'.$c[$index%3].'</div>';
}

  
$("div.right").each(function() {
    var $el =$(this);
    var $parent = $(this).prevAll('.right');
    var offset = 0;
    if($parent.height() > 0) {
    offset = parseFloat($el.offset().top - ($parent.outerHeight()+$parent.offset().top)-parseFloat($el.css('marginBottom')));
    if(offset > 0)
    $el.css('margin-top','-'+offset+'px');
    }
});