Codeforces 546A - Soldier and Bananas

A. Soldier and Bananas

time limit per test

1 second

memory limit per test

256 megabytes

input

standard input

output

standard output

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?

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.

Sample test(s)

input

3 17 4

output

13

Solution:

#include<stdio.h>
int main()
{
    int k, n, w,sum=0,i=1; 
    scanf("%d %d %d",&k,&n,&w);
    for(;0< w;w--,i++)
    {
        sum=sum+(k*i);
    }
    if(sum>n)printf("%d\n",sum-n); 
    else printf("0\n"); 
 
    return 0;
}