Problem:
Score : 100 points

Problem Statement

We have two bottles for holding water.

Bottle 1 can hold up to A milliliters of water, and now it contains B milliliters of water.

Bottle 2 contains C milliliters of water.

We will transfer water from Bottle 2 to Bottle 1 as much as possible.

How much amount of water will remain in Bottle 2?

Constraints

All values in input are integers.

1 \leq B \leq A \leq 20

1 \leq C \leq 20

Input

Input is given from Standard Input in the following format:

A B C

Output

Print the integer representing the amount of water, in milliliters, that will remain in Bottle 2.

Sample Input 1

6 4 3

Sample Output 1

1

We will transfer two milliliters of water from Bottle 2 to Bottle 1, and one milliliter of water will remain in Bottle 2.

Sample Input 2

8 3 9

Sample Output 2

4

Sample Input 3

12 3 7

Sample Output 3

0

Solution in C# (Mono 4.6.2.0) (judge verdict: Runtime Error)

using System;
namespace Answer {
  class Program {
    public static void Main(string[] args) {
      var N = int.Parse(Console.ReadLine());
      var digitNum = N.ToString().Length;
      var ans = 0;
      int init, last;
      var digit = 1;
      var lessThanN = true;
      while (lessThanN) {
        init = (int)Math.Pow(10, digit - 1);
        last = (int)Math.Pow(10, digit) - 1;
        if (init > N) break;
        if (last >= N) {
          lessThanN = false;
          last = N;
        }
        ans += (int)last - (int)init + 1;
        digit += 2;
      }
      Console.WriteLine(ans);
    }
  }
}