function openTab(evt, tabName) {
    var i, tabcontent, tablinks;
    tabcontent = document.getElementsByClassName("tabcontent");
    for (i = 0; i < tabcontent.length; i++) {
        tabcontent[i].style.display = "none";
    }
    tablinks = document.getElementsByClassName("tablinks");
    for (i = 0; i < tablinks.length; i++) {
        tablinks[i].className = tablinks[i].className.replace(" active", "");
    }
    document.getElementById(tabName).style.display = "block";
    evt.currentTarget.className += " active";
}

function increment() {
    var passengers = document.getElementById("passengers");
    var value = parseInt(passengers.value, 10);
    if (value < 50) {
        passengers.value = value + 1;
    }
}

function decrement() {
    var passengers = document.getElementById("passengers");
    var value = parseInt(passengers.value, 10);
    if (value > 1) {
        passengers.value = value - 1;
    }
}