from math import *

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

r,x,y,a,b = map(int,input().split())
z = calc(x,y,a,b)
if z%(2*r)>0:
    print(int(z//(2*r)+1))
else:
    print(int(z//(2*r)))