if (age <= 0) {
    return "Invalid age.";
}

else if(age < 6) {

    return "You are not allowed to watch Deadpool after 6.00pm.";
}

else if(age < 17) {

    return "You must be accompanied by a guardian who is 21 or older.";
}
else if(age < 25) {
    return "You are allowed to watch Deadpool, right after you show some ID.";
}
else if(age >= 25) {

    return "Yay! You can watch Deadpool with no strings attached!";
}
else {
    return "Invalid age.";
}