$(document).ready(function()
{
    $('#country').on('autocompleteselect', function(e, ui)
    {
        var ultimo = $('#country').val();
        var disctricts = 'xajax.php?variavel=distritos&q='+ultimo;

        $("#distritos").autocomplete({
            source: disctricts
        });
    });

var ultimo = $('#country').val(ui.item.value);

var ultimo = $('#country').val();

$('#pais').on('autocompleteselect', function (e, ui) {
    var ultimo = ui.item.value;
    // ...etc

$('#pais').on('autocompletechange', function () {
    var ultimo = $(this).val();
    // ... etc