try:
	r,x1,y1,x2,y2 = map(int,raw_input().split())
	dist = ((x2-x1)**2+(y2-y1)**2)**0.5
	steps = 0
	while dist >= 2*r:
		dist-=(2*r)
		steps += 1
	if dist==0:
		print steps
	else:
		print 1+steps
except:
	pass
