import sys
s= raw_input().split(" ")
r  = int(s[0])
x1  = int(s[1])
y1  = int(s[2])
x2  = int(s[3])
y2  = int(s[4])
import math

def calculateDistance(x1,y1,x2,y2):
     dist = math.sqrt((x2 - x1)**2 + (y2 - y1)**2)
     return dist

d = calculateDistance(x1,y1,x2,y2)
r *= 2 
if d == 0 :
	print 0
	exit()
elif d < (r):
	print 2
	exit()
else:
	#print int((d) / r) 
	if int((d) / r)  != (d) / r:
		print int((d) / r) + 1
	else:
		print int((d) / r) 
	
	exit()