import java.util.*; import java.util.Scanner; import java.io.FileNotFoundException; import java.io.File; class CatchTheUFO{ public static void main(String args[]){ Scanner scan = new Scanner(System.in); 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); } }