if (localStorage.getItem('classHidden') === true) {
    $('.A').addClass('hidden');
} else if (localStorage.getItem('classHidden') === false) {
    $('.A').removeClass('hidden');
}

$(".X").click(function () {
    localStorage.setItem('classHidden', false);
    $('.A').removeClass('hidden');
});
 
$(".Y").click(function () {
    localStorage.setItem('classHidden', true);
    $('.A').addClass('hidden');
});