#include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>
#include <fstream>
#include <queue>
#include <complex>

#define INF_MIN 100000000
#define INF 1145141919
#define INF_MAX 2147483647
#define LL_MAX 9223372036854775807
#define EPS 1e-10
#define PI acos(-1)
#define LL long long

using namespace std;

int x, y;
int xx1, yy1;

int main(){

  cin >> x >> y;
  cin >> xx1 >> yy1;
  
  int ans = max(x, y);

  if(x == y && xx1 == yy1 && x*xx1 > 0 && y*yy1 > 0){
    ans += 2;
  }

  cout << ans << endl;

  return 0;

}