function solution(price, money, count) {
const cost = Array(count).fill(price).reduce((acc, cur, idx) => acc + cur + cur * idx, 0);
return money - cost >= 0 ? 0 : cost - money;
}
function solution(price, money, count) {
const tmp = price * count * (count + 1) / 2 - money;
return tmp > 0 ? tmp : 0;
}