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
def calcCost (cost, ith_banana, total_bananas) :
        ith_banana += 1;
        if(ith_banana >= total_bananas) :
                return (ith_banana * cost);

        return (cost * ith_banana) + calcCost(cost, ith_banana, total_bananas);

inp = input();
arr = inp.split(' ');
initCost = int(arr[0]);
currentMoney = int(arr[1]);
totalBananas = int(arr[2]);
x = 0;
ith_banana = 0;
currBanana = 0;
while(ith_banana < totalBananas) :
        currBanana = min((currBanana+100),totalBananas);
        totalCost = calcCost(int(initCost), ith_banana, currBanana);
        x += totalCost;
        ith_banana += 100;

x -= int(currentMoney);
if (x > 0) :
        y = x;
else :
        y = 0;
print(str(y));

