B - Soldier and Bananas

标签：输出   mes   script   name   ini   friend   from   c代码   std   

Problem description

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·kdollars 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?

Input

The first line contains three positive integers k,?n,?w (1??≤??k,?w??≤??1000, 0?≤?n?≤?10⁹), the cost of the first banana, initial number of dollars the soldier has and number of bananas he wants.

Output

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.

Examples

3 17 4

13
解题思路：等差数列求前w项和，如果够钱，则输出0，否则就输出需要借钱的数目，水过。
AC代码：

 1 #include<bits/stdc++.h>
 2 using namespace std;
 3 int main(){
 4     int k,n,w,r;
 5     cin>>k>>n>>w;
 6     r=((1+w)*w/2)*k;
 7     if(r<=n)cout<<‘0‘<<endl;
 8     else cout<<(r-n)<<endl;
 9     return 0;
10 }

B - Soldier and Bananas

标签：输出   mes   script   name   ini   friend   from   c代码   std   

原文地址：https://www.cnblogs.com/acgoto/p/9128882.html