A soldier wants to buy $*w*$ bananas in the shop. He has to pay $*k*$ dollars for the first banana, $2*k*$ 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 $*k*, *n*, *w*$ ($1  ≤  *k*, *w*  ≤  1000$, $0 ≤ *n* ≤ 10^{9}$), 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 $0$.