Soldier and Bananas Problem !!!

 Problem 31: Soldier and Bananas

Problem Reference: Codeforces

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.

Solution: 

1. k,n,w = input().split()
2. w1 = 0
3. for i in range(1,int(w)+1):
4. w1 = w1 + i * int(k)
5.  
6. w2 = w1 - int(n)
7. if w2 > 0:
8. print(w2)
9. else:
10. print("0")

The above solution is in python language.

Examples

input

3 17 4

output

13

1.