Hi, I'm trying to dynamically add a span to an ol, where the counter should be in letters. eg: A result B result C result etc etc

I've got this code which is great for using numbers but I've no idea what to do to it to make the numbers into letters

jQuery(document).ready( function() {
    jQuery('.results ol').each(function () {
       jQuery(this).find('li').each(function (i) {
           i = i+1;
           jQuery(this).prepend('<span class="marker">' + i + '</span>');
       });
    });
});

Any help is greatly appreciated!