#include <iostream>
#include <cstring>
#include <algorithm>

using namespace std;

const int N = 10, M = 1000010;

typedef pair<int, int> PII;

int dx[] = {0,  1,  2,  2,  1, -1, -2, -2, -1};
int dy[] = {0,  2,  1, -1, -2, -2, -1,  1,  2};

int step[N][N];
bool map[N][N];
PII q[M];

int main(){
    int xx, yy, aa, bb;
    cin >> xx >> yy >> aa >> bb;

    step[xx][yy] = 0;
    map[xx][yy] = true;
    q[0] = {xx, yy};

    int hh = 0, tt = 0;
    while (hh <= tt){
        int x = q[hh].first, y = q[hh].second;
        hh ++;
        for (int i = 1; i <= 8; i ++){
            int a = x + dx[i], b = y + dy[i];
            if (a >= 1 && a <= 8 && b >= 1 && b <= 8 && !map[a][b]){
                map[a][b] = true;
                q[ ++ tt] = {a, b};
                step[a][b] = step[x][y] + 1;
            }
        }
    }

    cout << step[aa][bb];

    return 0;
}