from sys import*
import math
def distance(x,y,x1,y1):
	dis = math.sqrt(((x1-x)*(x1-x)) + ((y1-y)*(y1-y)))
	return dis
def steps(r,x,y,x1,y1):
	if((distance(x,y,x1,y1)%(2*r)) == 0):
		return int(distance(x,y,x1,y1)/(2*r))
	else:
		return int(distance(x,y,x1,y1)/(2*r)) +1
a = [0,0,0,0,0]
a = list(map(int,input().strip().split()))[:5]
r,x,y,x1,y1 = a[0],a[1],a[2],a[3],a[4]
print(steps(r,x,y,x1,y1))