#include <cstdio>
#include <algorithm>
#include <stack>
#include <queue>
#include <deque>
#include <vector>
#include <string>
#include <string.h>
#include <cstdlib>
#include <ctime>
#include <cmath>
#include <map>
#include <set>
#include <iostream>
#include <sstream>
#include <numeric>
#include <cctype>
#define fi first
#define se second
#define rep(i,n) for(int i = 0; i < n; ++i)
#define rrep(i,n) for(int i = 1; i <= n; ++i)
#define drep(i,n) for(int i = n-1; i >= 0; --i)
#define gep(i,g,j) for(int i = g.head[j]; i != -1; i = g.e[i].next)
#define each(it,c) for(__typeof((c).begin()) it=(c).begin();it!=(c).end();it++)
#define rng(a) a.begin(),a.end()
#define maxs(x,y) x = max(x,y)
#define mins(x,y) x = min(x,y)
#define pb push_back
#define sz(x) (int)(x).size()
#define pcnt __builtin_popcount
#define snuke srand((unsigned)clock()+(unsigned)time(NULL));
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
typedef vector<int> vi;
typedef vector<vi> vvi;
inline int in() { int x; scanf("%d",&x); return x;}
inline void priv(vi a) { rep(i,sz(a)) printf("%d%c",a[i],i==sz(a)-1?'\n':' ');}

const int MX = 100005, INF = 1000010000;
const ll LINF = 1000000000000000000ll;
const double eps = 1e-10;

int dist(int a, int b) {
  a = abs(a);
  b = abs(b);
  return max(a,b);
}

bool f(int x, int y) {
  int b = 0;
  if (x<0) b ^= 1;
  if (y<0) b ^= 1;
  if(b) return false;
  return abs(x) > abs(y);
}

int main(){
  int a,b,c,d;
  cin >> a >> b >> c >> d;
  int ans = dist(a,b);
  // if (a == 0 && c == 0 && f(b,d)) ans++;
  // if (b == 0 && d == 0 && f(a,c)) ans++;
  if (a == b && c == d && f(a,c)) ans++;
  if (a == -b && c == -d && f(a,c)) ans++;
  cout<<ans<<endl;
  return 0;
}