Find combinations of input value that can win 1st, 2nd, 3rd prize.

combinations.js

function combinations(n) {
    if (n < 0) {
        return 0;
    } else if (n < 3) {
        return n;
    }
    return n * (n - 1) * (n - 2);
}

console.log(combinations(8)) // (8 - 1 = 7) * (8 - 2 = 6) = (42 * 8) = 336
console.log(combinations(6)) // (6 - 1 = 5) * (6 - 2 = 4) = (20 * 6) = 120
console.log(combinations(4)) // (4 - 1 = 3) * (4 - 2 = 2) = (6 * 4) = 24
console.log(combinations(3)) // 6