Grasshop.java

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
 
 
public class Grasshop {
 
	private static int [][] pole;
	public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String str;
		String[] radek;
		int x,y,gx,gy,lx,ly;
 
		while((str = br.readLine()) != null){
			radek = str.split(" ");
			x = Integer.parseInt(radek[0]);
			y = Integer.parseInt(radek[1]);
			gx = Integer.parseInt(radek[2]);
			gy = Integer.parseInt(radek[3]);
			lx = Integer.parseInt(radek[4]);
			ly = Integer.parseInt(radek[5]);
 
			pole = new int [x][y];
 
			rek(gx-1, gy-1, 1);
			System.out.println(pole[lx-1][ly-1] == 0 ? "impossible" : pole[lx-1][ly-1]-1);
		}
 
	}
 
	private static void rek(int x, int y, int cena)
	{
		if (pole[x][y] == 0 || pole[x][y] > cena)
			pole[x][y] = cena;
		else
			return;
		//System.out.println(x+" "+y+" "+cena);
		if (isValid(x+1, y+2))
			rek(x+1, y+2, cena+1);
		if (isValid(x+1, y-2))
			rek(x+1, y-2, cena+1);
		if (isValid(x-1, y+2))
			rek(x-1, y+2, cena+1);
		if (isValid(x-1, y-2))
			rek(x-1, y-2, cena+1);
		if (isValid(x+2, y+1))
			rek(x+2, y+1, cena+1);
		if (isValid(x+2, y-1))
			rek(x+2, y-1, cena+1);
		if (isValid(x-2, y+1))
			rek(x-2, y+1, cena+1);
		if (isValid(x-2, y-1))
			rek(x-2, y-1, cena+1);
	}
 
	private static boolean isValid(int x, int y)
	{
		return 	x >= 0 &&
				x < pole.length &&
				y >= 0 &&
				y < pole[0].length;
	}
 
}