You can achieve this by using javascript. Find out the biggest height of the 4 divs and make all of them at the same height like the biggest one.
Here is the code:
$( document ).ready(function() {
var heights = $(".well").map(function() {
return $(this).height();
}).get();
maxHeight = Math.max.apply(null, heights);
$(".well").height(maxHeight);
});
edit history: changed the ‘,’ sign into ‘;’ sign