프로그래머스 - 부족한 금액 계산하기 (JAVA)

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class Solution {
    public long solution(int price, int money, int count) {
        long answer = 0;

        for(int i = 1; i <= count; i++){
            answer += (long) i * price;
        }

        if(money >= answer){
            return 0;
        }else{
            return answer - money;
        }
    }
}