import java.util.*;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int x = sc.nextInt();
    int y = sc.nextInt();
    int r = sc.nextInt();
    int a = 0;
    for(int i = 1; i <= 200; i++) {
      if(i * i > 2 * r * r) {
        a = i;
        break;
      }
    }
    int s = Math.abs(Math.min(0, x - a - y));
    int t = Math.abs(Math.min(0, x - a + y));
    int u = Math.abs(Math.max(0, x + a + y));
    int v = Math.abs(Math.max(0, x + a - y));
    int ans = Math.max(Math.max(s, t), Math.max(u, v));
    System.out.println(ans);
  }
}