#include "iostream"
#include "climits"
#include "list"
#include "queue"
#include "stack"
#include "set"
#include "functional"
#include "algorithm"
#include "math.h"
#include "utility"
#include "string"
#include "map"
#include "unordered_map"
#include "iomanip"
#include "random"

using namespace std;
const long long int MOD = 1000000007;
list<long long int> Prime(int M) {
	list<long long int>P;
	P.push_back(2);
	P.push_back(3);
	for (int i = 5; i <= M; i += 6) {
		bool flag = true;
		for (auto j : P) {
			if (i%j == 0) {
				flag = false;
				break;
			}
		}
		if (flag)P.push_back(i);
		flag = true;
		for (auto j : P) {
			if ((i + 2) % j == 0) {
				flag = false;
				break;
			}
		}
		if (flag)P.push_back(i + 2);
	}
	return P;
}

long long int N, K, Q, M;
long long int ans;

long long int sx, sy, gx, gy;

int main() {
	ios::sync_with_stdio(false);
	cin >> sx >> sy;
	cin >> gx >> gy;
	ans = max(abs(sx), abs(sy));
	if (abs(sx) == abs(sy)) {
		if (abs(gx) == abs(gy)) {
			if (sx < 0 && sy < 0 && gx < 0 && gy < 0 && sx < gx&&sy < gy)ans++;
			if (sx > 0 && sy > 0 && gx > 0 && gy > 0 && sx > gx&&sy > gy)ans++;
			if (sx > 0 && sy < 0 && gx > 0 && gy < 0 && sx > gx&&sy < gy)ans++;
			if (sx < 0 && sy > 0 && gx < 0 && gy > 0 && sx < gx&&sy > gy)ans++;
		}
	}
	cout << ans << endl;
	return 0;
}