#include <iostream>
using namespace std;
//abÊÇÖÕµã 
int dx[8] = {-2, -1, 1, 2, 2, 1, -1, -2};
int dy[8] = {1, 2, 2, 1, -1, -2, -2, -1};
int step[9][9];

void dfs(int _a, int _b, int _n, int _m){
	if(_n > 8 || _n < 1 || _m < 1 || _m > 8) return;
	if(_n == _a && _m == _b) return;
	for(int i = 0; i < 8; i++){
		int nx = _n + dx[i];
        int ny = _m + dy[i];
        
        if (nx >= 1 && nx <= 8 && ny >= 1 && ny <= 8) {
            int stepnew = step[_n][_m] + 1;
            if (step[nx][ny] == 0 || stepnew < step[nx][ny]) {
                step[nx][ny] = stepnew;
                dfs(_a, _b, nx, ny);
            }
        }
	}
}

int main(){
	int a, b, n, m;
	cin >> n >> m >> a >> b;
	step[n][m] = 0; 
	dfs(a, b, n, m);
	cout << step[a][b] << endl;
	return 0;
}