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
#                           जय श्री राम

import sys; import math; from collections import *
# sys.setrecursionlimit(10**6)

def get_ints(): return map(int, input().split())
def get_list(): return list(get_ints())
def printspx(*args): return print(*args, end="")
def printsp(*args): return print(*args, end=" ")

UGLYMOD = int(1e9+7); SEXYMOD = 998244353; MAXN = int(1e5)

#sys.stdin  = open("input.txt","r"); sys.stdout = open("output.txt","w")

# for _testcases_ in range(int(input())):
k, n, w = get_ints()
print(max(0, (k*(w*(w+1))//2) - n))


'''
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