#include <stdio.h>
#include <math.h>

int main(void)
{
	int x,y,l,s=0;
	scanf("%d%d%d",&x,&y,&l);
	if(x!=0)s++;
	if(y<0&&x==0)s+=2;
	else if(y<0)s++;
	s+=(fabs(x)+fabs(y))/l;
	if((int)(fabs(x)+fabs(y))%l)s++;
	printf("%d",s);
	return 0;
}