def amr(r,x1,y1,x2,y2):
	x = x1-x2
	y = y1-y2
	dist = (x**2 + y**2)**(.5)
	i = 0 
	while dist > 0:
		dist -= 2*r
		i += 1
	return i
a = list(map(int, input().split()))	
print(amr(a[0],a[1],a[2],a[3],a[4]))