Easter Party

function easterParty(input) {
    let guest = Number(input.shift());
    let envelope = Number(input.shift());
    let budget = Number(input.shift());

    let sum = guest * envelope;

    if (guest >= 10 && guest <= 15) {
        sum *= 0.85;
    } else if (guest > 15 && guest <= 20) {
        sum *= 0.8;
    } else if (guest > 20) {
        sum *= 0.75;
    }
    sum += budget / 10;

    if (budget >= sum) {
        console.log(`It is party time! ${(budget - sum).toFixed(2)} leva left.`);
    } else {
        console.log(`No party! ${(sum - budget).toFixed(2)} leva needed.`);
    }
}