grasshop.c

#include <stdio.h>
#include <math.h>
 
int R,C, Lr, Lc, Gr, Gc;
 
int get_dist(int a, int b, int x, int y)
{
	return fabs(x-a) + fabs(y-b);
}
 
int main()
{
	while(scanf("%d %d %d %d %d %d", &R,&C,&Gr,&Gc,&Lr,&Lc) == 6)
	{
		int d = get_dist(Gr, Gc, Lr, Lc);
		if (R == 1 || C == 1) {
			printf("impossible\n");
		}
		else if (R == 2 || C == 2) {
			if (d % 3 == 0) {
				printf("%d\n", d/3);
			} else printf("impossible\n");
		} else {
			switch(d) {
				case 1:
					printf("3\n");
					break;
				case 2:
					printf("2\n");
					break;
				case 3:
					printf("1\n");
					break;
				case 4:
					printf("4\n");
					break;
				case 5:
					printf("3\n");
					break;
			}
			if (d > 5) {
				int result = (d % 3) > 0 ? 1 : 0;
				result += d/3;
				printf("%d\n", result);
			}
		}
	}
	return 0;
}