#include <stdio.h>
#include <iostream>
#include <chrono>
using namespace std;

struct Point {
	int x;
	int y;
};

Point start = { 0, 0 };
Point goal;
Point obst;

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

	int cnt = 0;

	cin >> goal.x >> goal.y >> obst.x >> obst.y;

	/* 斜めに進んで残った分を真っすぐ進む */
	if (goal.x >= goal.y) {
		cnt += goal.y + (goal.x - goal.y);
	}
	else {
		cnt += goal.x + (goal.y - goal.x);
	}
	/*斜めに進んで障害物にぶつかる場合はコスト+1（真っすぐ進む場合は変わらない）*/
	if ((obst.x < goal.x) && (obst.y < goal.y)) {
		if (obst.x == obst.y) {
			cnt++;
		}
	}
	cout << cnt << endl;
}