import java.util.*;
import java.lang.*;
import java.io.*;

class Main
{
	public static void main (String[] args) throws java.lang.Exception
	{
		long m, n, a, b;
		Scanner in = new Scanner(System.in);
		m = in.nextLong();
		n = in.nextLong();
		a = in.nextLong();
		b = in.nextLong();
    	long dm = ((a + 1)/2 - 1) %m - ((b + 1)/2 - 1) % m;
    	long dn = (a - 1)/(2 * m) - (b - 1)/(2 * m);
    	long o = dm * dn < 0? Math.min(Math.abs(dm), Math.abs(dn)) : 0;
    	long k = dm > 0? 1: -1;
    	a += 2*k*o*(m - 1);
    	System.out.print( ((a + b) % 2 == 0? 0: Math.max(a, b) % 2 == 0? 1: -1) + 2*(Math.abs(dm) + Math.abs(dn) - o));

	}
}