#include <iostream>
#include <vector>
#include <cstdlib>
#include <queue>

using namespace std;

#define x first
#define y second

const int dx[8] = {-2,-1,1,2,2,1,-1,-2};
const int dy[8] = {1,2,2,1,-1,-2,-2,-1};

const int INF = 1000000000;

bool is_correct(int x,int y){
    return x >= 0 && x < 8 && y >= 0 && y < 8;
}

int main(){
    pair<int,int> start,finish;
    cin >> start.x >> start.y >> finish.x >> finish.y;
    queue<pair<int,int>> q;
    q.push({start.x - 1,start.y - 1});
    vector <vector<int>> dist(8,vector<int>(8,INF));
    dist[start.x - 1][start.y - 1] = 0;

    while (!q.empty()){
        auto p = q.front();
        q.pop();
        for (int i = 0; i < 8; i++){
            int x = p.x + dx[i];
            int y = p.y + dy[i];
            if (is_correct(x,y) && dist[x][y] > dist[p.x][p.y] + 1){
                dist[x][y] = dist[p.x][p.y] + 1;
                q.push({x,y});
            }
        }
    }

    int d = dist[finish.x - 1][finish.y - 1];
    if (d%2 == 0 && d != INF)
    {
        cout << d/2 << endl;
    }
    else{
        int min_dist = INF;
        for (int i = 0; i < 8; i++)
        {
            int x = finish.x + dx[i];
            int y = finish.y + dy[i];
            if (is_correct(x,y) && dist[x][y] % 2 == 0 && dist[x][y] < min_dist)
                min_dist = dist[x][y];
        }
        if (min_dist != INF)
            cout << min_dist/2 << endl;
        else
            cout << -1 << endl;
    }

}