Gromozeka loves valerian very much. On his home planet Chumaroza you can buy for k chumriks (local currency) the first package of valerian, for 2·k chumriks - the second and so on (in other words, ith packing you have to pay i·k chumrikov). Gromozek wants to buy w packages of valerian. He has n chumriks. How many chumriks will he have to take on credit from the chumaroz bank in order to buy w packages of valerian?
Input
The first line contains three positive integers k, n, w (1 <= k, w< /code> <= 1000, 0 <= n <= 109) , the cost of the first package, Gromozeka's initial number of chumaroziki and the number of packages of valerian he wants to buy.
Output
Print a single integer - the number of chumaroziks that Gromozeka needs to borrow from the bank. If you don't need to take a loan, print 0.
Examples
| # |
Input |
Output |
| 1 |
3 17 4 |
13 |