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.

Examples

Input

3 17 4


Output

13
#!/bin/python3

import math
import os
import random
import re
import sys

# Complete the matrixRotation function below.
def function(m,n,r):
    i=m
    while r!=1:
        i=i + (m*r)
        r=r-1
    diff= i-n
    if diff>=0:
        print(diff)
    else:
        print(0)


mnr = input().rstrip().split()

m = int(mnr[0])

n = int(mnr[1])

r = int(mnr[2])

function(m,n,r)
