Soldier and Bananas
题意翻译
有个士兵想买 $w$ 个香蕉,第 $i$ 个香蕉需支付 $ki$ 元。
现在他手里有 $n$ 元,问他至少要借多少钱才能买到 $w$ 个香蕉?(不需要借钱输出 $0$)。
输入一行三个整数 $n$, $k$, $w$, 含义如题面。
题目描述
A soldier wants to buy $ w $ bananas in the shop. He has to pay $ k $ dollars for the first banana, $ 2k $ dollars for the second one and so on (in other words, he has to pay $ i·k $ dollars for the $ i $ -th banana).
He has $ n $ dollars. How many dollars does he have to borrow from his friend soldier to buy $ w $ bananas?
输入输出格式
输入格式
The first line contains three positive integers $ k,n,w $ ( $ 1<=k,w<=1000 $ , $ 0<=n<=10^{9} $ ), the cost of the first banana, initial number of dollars the soldier has and number of bananas he wants.
输出格式
Output one integer — the amount of dollars that the soldier must borrow from his friend. If he doesn't have to borrow money, output $ 0 $ .
输入输出样例
输入样例 #1
3 17 4
输出样例 #1
13