Snacks

Time limit1sMemory limit256 MB

Summary

Compute K times N minus M, or zero when the money on hand covers the total snack price.

Level: Easy1 of 10
Topics: Math
Solved: No attempts yet

Problem

Dongsu wants to buy snacks at a bakery. When his own money is not enough, he gets the difference from his parents. One snack costs $K$ won, he wants $N$ snacks, and he currently holds $M$ won.

The snacks cost $K \times N$ won in total. If that total is larger than $M$ , he has to get the difference $K \times N - M$ won from his parents, and if $M$ is at least the total, he gets nothing. For example, buying 4 snacks at 30 won each while holding 100 won needs 20 won, and buying 6 snacks at 20 won each while holding 120 won needs nothing.

Given $K$ , $N$ , and $M$ , find how much money Dongsu has to get from his parents.

Input

The first line contains the price of one snack $K$ , the number of snacks $N$ , and the money Dongsu holds $M$ , separated by spaces. All three are integers with $1 \le K, N \le 1000$ and $1 \le M \le 100000$ .

Output

Print on the first line the amount Dongsu has to get from his parents. Print 0 when he needs nothing.

Examples4

Example 1
Input
```
300 4 1000
```
Expected output
```
200
```
Example 2
Input
```
250 2 140
```
Expected output
```
360
```
Example 3
Input
```
20 6 120
```
Expected output
```
0
```
Example 4
Input
```
20 10 320
```
Expected output
```
0
```