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

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