#include <iostream>
int a, b, x, y;

int main() {
  std::cin >> a >> b >> x >> y;
  int path1;
  int path2;
  int path3;
  int ans;
  path1 = std::abs(a - b);
  path2 = std::abs(a - x) + std::abs(y - b);
  path3 = std::abs(a - y) + std::abs(x - b);
  ans = path1;
  if (path2 < ans) {
    ans = path2;
  }
  if (path3 < ans) {
    ans = path3;
  }
  std::cout << ans << std::endl;
}