#include <bits/stdc++.h>
using namespace std;
typedef pair<int,int> P;
const int INF = 1e9;

int main()
{
    int x1,y1,x2,y2;
    cin >> x1 >> y1 >> x2 >> y2;

    int board[y1+1][x1+1];
    for(int i = 0; i < y1+1; i++) for(int j = 0; j < x1+1; j++) board[i][j] = INF;
    board[0][0] = 0;
    int dx[] = {-1,0,1,-1,1,-1,0,1},dy[] = {1,1,1,0,0,-1,-1,-1};
    queue<P> que;
    que.push(P(0,0));

    while(que.size()){
        P xy = que.front();
        if(xy.first == y1 && xy.second == x1) break;
        que.pop();
        for(int i = 0; i < 8; i++){
            int nx = xy.second + dx[i];
            int ny = xy.first + dy[i];
            if(nx >= 0 && nx <= x1 && ny >= 0 && ny <= y1 && board[ny][nx] == INF && !(nx == x2 && ny == y2)){
                board[ny][nx] = board[xy.first][xy.second] + 1;
                que.push(P(ny,nx));
            }
        }
    }

    cout << board[y1][x1] << endl;

    return 0;
}