class Solution {
    public long solution(int price, int money, int count) {
        long answer =0;
        
        long mo=0;
        
        for(int i=1; i<=count; i++){
            mo+=price*i;
            
        }
        
        if(money>=mo){
            return 0;
        }else{
            answer = mo-money;
        }
        
        
        
        return answer;
    }
}