import math
r,x,y,x1,y1=map(int,input().split())

yd=(y1-y)*(y1-y)
xd=(x1-x)*(x1-x)
#print(xd,yd)
pd=math.sqrt(yd+xd)
#print("pd = ",pd)
if (pd//(r*2)==pd/(r*2)):
	print(int(pd//(r*2)))
else:
	print(int(pd//(r*2)+1))
