function v() {
        var required = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 24];
        var hasError = false;

    	for (var i = 0; i < required.length; i++) {
        	var de = document.getElementById('f' + required[i]);
            if (!de) continue;

            var val = $(de).val();
            var isCheckbox = (String($(de).attr("type")).toLowerCase() == "checkbox");
            var notChecked = false;

            if (isCheckbox && !$(de).attr('checked')) {
                notChecked = true;
            }

            if ((!isCheckbox && val.length == 0) || (isCheckbox && notChecked)) {
            	$("#f" + required[i]).parent().addClass('error');
            	hasError = true;
            } else {
            	$("#f" + required[i]).parent().removeClass('error');
            }
        }

	if (hasError) {
		alert("Proszę poprawnie wypełnić formularz");
	}

	return !hasError;
}