import math
arr=list(map(int,input().split()))
r,x,y,x1,y1=arr[0],arr[1],arr[2],arr[3],arr[4]
d=math.sqrt((x-x1)**2+(y-y1)**2)
if d%(r*2)==0:
	print(int(d//(2*r)))
elif d<4*r:
	print(2)
else:
	step=0
	while d>4*r:
		d=d-2*r
		step+=1
	print(step+2)