#include <string>
#include <vector>
#include <algorithm>
#include <numeric>
#include <set>
#include <map>
#include <queue>
#include <iostream>
#include <sstream>
#include <cstdio>
#include <cmath>
#include <ctime>
#include <cstring>
#include <cctype>
#include <cassert>
#include <limits>
#include <functional>
#define rep(i,n) for(int (i)=0;(i)<(int)(n);++(i))
#define rer(i,l,u) for(int (i)=(int)(l);(i)<=(int)(u);++(i))
#define reu(i,l,u) for(int (i)=(int)(l);(i)<(int)(u);++(i))
#if defined(_MSC_VER) || __cplusplus > 199711L
#define aut(r,v) auto r = (v)
#else
#define aut(r,v) __typeof(v) r = (v)
#endif
#define each(it,o) for(aut(it, (o).begin()); it != (o).end(); ++ it)
#define all(o) (o).begin(), (o).end()
#define pb(x) push_back(x)
#define mp(x,y) make_pair((x),(y))
#define mset(m,v) memset(m,v,sizeof(m))
#define INF 0x3f3f3f3f
#define INFL 0x3f3f3f3f3f3f3f3fLL
using namespace std;
typedef vector<int> vi; typedef pair<int,int> pii; typedef vector<pair<int,int> > vpii; typedef long long ll;
template<typename T, typename U> inline void amin(T &x, U y) { if(y < x) x = y; }
template<typename T, typename U> inline void amax(T &x, U y) { if(x < y) x = y; }

int main() {
	int x, y, x2, y2;
	cin >> x >> y >> x2 >> y2;
	vi v;
	rer(dx,-1,1)v.pb(0+dx);
	rer(dx,-1,1)v.pb(x+dx);
	rer(dx,-1,1)v.pb(y+dx);
	rer(dx,-1,1)v.pb(x2+dx);
	rer(dx,-1,1)v.pb(y2+dx);
	sort(all(v));
	v.erase(unique(all(v)), v.end());
	priority_queue<pair<ll,pii> > q;
	q.push(mp(-0LL, mp(x, y)));
	set<pii> vis;
	while(!q.empty()) {
		ll t = -q.top().first;
		pii p = q.top().second;
		q.pop();
		if(vis.count(p)) continue;
		vis.insert(p);
//		cerr << p.first << ", " << p.second << ": " << t << endl;
		if(p == mp(0, 0)) {
			cout << t << endl;
			return 0;
		}
		each(i, v) each(j, v) {
			pii a(*i, *j);
			if(a == mp(x2, y2)) continue;
			if(abs((int)(lower_bound(all(v),a.first)- lower_bound(all(v),p.first)))>1)continue;
			if(abs((int)(lower_bound(all(v),a.second)- lower_bound(all(v),p.second)))>1)continue;
			ll d = max(abs(a.first-p.first), abs(a.second-p.second));
			q.push(mp(-(t + d), a));
		}
	}
	return 0;
}