import java.util.*;
import java.util.Scanner;
import java.io.FileNotFoundException;
import java.io.File;

class CatchTheUFO{
  public static void main(String args[]){
    try{
      File file = new File("test.txt");
      Scanner scan = new Scanner(file);


      int x = Integer.parseInt(scan.next());
      int y = Integer.parseInt(scan.next());
      int r = Integer.parseInt(scan.next());

      double ans_d = Math.sqrt(2) * r;
      ans_d = Math.ceil(ans_d);
      int ans = (int) ans_d;

      System.out.println(ans);

    }catch(FileNotFoundException e){
      System.out.println(e);
    }
  }
}