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
#!/usr/bin/pypy3

from sys import stdin

def readInts(): return map(int,stdin.readline().strip().split())

def solve(k,n,w):
    w2 = w
    x = 1
    while w2>0:
        n -= x*k
        x += 1
        w2 -= 1
    return max(0,-n)

def run():
    k,n,w = readInts()
    print(solve(k,n,w))
        
run()
