#include <iostream>
#include <cstdio>
#include <cmath>
using namespace std;
int x,sum=0;
double a,b,c,d,j,s1=0,s2,w,y,z;
int main(void)
{  
	freopen ("sars.in","r",stdin);
	freopen ("sars.out","w",stdout);
	cin>>a>>b>>c>>d;
	w=c;
	s2=-d;
	for (x=1;x<40;x++) 
	{
		w=(double)w/2;
		if (w<1) break;
	}
	w=x;
	for (x=0;x<w+1;x++)
	{
		s1+=d;
		s2+=d;
		if ((a-b-0.00001<=s1)&&(a+b+0.00001>=s2)) sum++;
		y=a+c;
		z=a-c;
		if (fabs(y-(double)((s1+s2+2*d)/2))>fabs(z-(double)((s1+s2+2*d)/2))) a=z;
			else a=y;
		c=(double)c/2;
	}
	printf("%d",sum);
	fclose(stdin);
	fclose(stdout);
	return 0;  
}