#include <iostream>
using namespace std;

int main(int argc, char *argv[]) {
	std::ios::sync_with_stdio(false);
	std::cin.tie(0);
	int cnt, gx, gy, ox, oy;

	cin >> gx >> gy >> ox >> oy;

	if (gx >= gy) {
		cnt += gy + (gx - gy);
	}
	else {
		cnt += gx + (gy - gx);
	}

	if ((ox < gx) && (oy < gy)) {
		if ((ox == oy) && (gx == gy)) {
			cnt++;
		}
	}

	cout << cnt << endl;
}