1 import java.util.Scanner;
 2 
 3 
 4 public class Main {
 5 
 6     public static int binarySearch(int a,int b,int c, int left, int right) {
 7         int m = left + (right - left) / 2;
 8 
 9         if((a - m) * (b - m) <= 0 || (a - m) * (c - m) <= 0 || (c - m) * (b - m) <= 0) {
10             return m;
11         } else if(a > m) {
12             return binarySearch(a, b, c, m + 1, right);
13         } else {
14             return binarySearch(a, b, c, left, m - 1);
15         }
16     }
17 
18     public static void main(String[] args) {
19         Scanner sc = new Scanner(System.in);
20         int k = sc.nextInt();
21         int a = sc.nextInt();
22         int b = sc.nextInt();
23         int c = sc.nextInt();
24         System.out.println(binarySearch(a, b, c, 1, (2 << k) - 1));
25     }
26 }