Bon Appétit

import java.util.Scanner;
import static java.lang.System.*;

public class Main {
  public static void main(String[] args) {
    Scanner scan = new Scanner(in);
    double n = scan.nextDouble();
    double k = scan.nextDouble();
    double r = 0;
    for (double i = 0; i < n; ++i) {
      double c = scan.nextDouble();
      if (i == k) continue;
      r += c;
    }
    double p = scan.nextDouble();
    r = p - r / 2;
    if (r == 0) {
      out.println("Bon Appétit");
    } else {
      out.println(r);
    }
  }
}