#include <stdio.h>

#include <iostream>

using namespace std;

int zhongjianzhi(int m ,int n,int curroot,int k){

  if(curroot == (m + n)/ 2)  return curroot;

  if(m > curroot && n < curroot) return curroot;

  else if (m> curroot && n > curroot){

    curroot = (curroot + (1<<k)) /2;

    zhongjianzhi(m,n,curroot,k);

  }

  else {

    curroot = (curroot + 0)/2;

    zhongjianzhi(m,n,curroot,k);

  }

}

int main(){

  int k,a,b,c;

  cin >> k;

  cin >>  a >>  b >>  c;

   int num = 0;

   int maxx = max(max(a,b),c);

   int minn = min(min(a,b),c);

   int curroot = 1<<(k-1);

   num = zhongjianzhi(maxx,minn,curroot,k);

   cout << num << endl;

   return 0;

}