#include <iostream>
#include <utility>
#include <memory>
#include <cmath>
using coord = std::pair<int, int>;

#ifndef BOOST_TEST_MAIN
int main(int const argc, char const** argv){
  long x, y, x2, y2;
  std::cin >> x >> y;
  std::cin >> x2 >> y2;
  coord dest = {x, y};
  coord king = {0, 0};
  auto p = std::make_shared<int>(king.first);
  auto q = std::make_shared<int>(king.second);

  double kdtilt = (double)y / (double)x; 
  double kotilt = (double)y2 / (double)x2;
  long double kdlen = y * y + x * x;
  long double kolen = y2 * y2 + x2 * x2;
  // std::cout << " kdtilt:" << kdtilt << " kdlen:" << kdlen << "\n";
  // std::cout << " kotilt:" << kotilt << " kolen:" << kolen << "\n";
    
  auto count = 0;

  // ナナメ一直線のときは1回ロス
  auto tiltcond = (kdtilt == 1.0 && kotilt == 1.0) || (kdtilt == -1.0 && kotilt == -1.0);
  if(tiltcond && kdlen > kolen){
    // std::cout << "eu";
    ++count;
  }


  count += std::max(x, y);
  std::cout << count;
}
#endif