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 getLines(num):
  inputLines = []
  for i in range(0,num):
    line = input()
    if line:
      inputLines.append(line)
    else:
        break
  return inputLines

def notZeroPow(num,p):
  return True if num >= 1 and num <= pow(10,p)  else False


def countRepeat(value,arr):
    count = 0
    for e in arr:
        if e == value:
            count += 1
    return count

lines = getLines(1)
arr = [int(e) for e in lines[0].split()]
result = 0

for i in range(1,arr[2]+1):
    result += arr[0] * i
  

result -= arr[1]
result = result if result > 0 else 0

print(result)