import math
    
r,x,y,x2,y2 = [int(s) for s in raw_input().split(" ")]

c2=(x2,y2)
c=(x,y)
d = math.sqrt((x-x2)**2 + (y-y2)**2)

steps =math.trunc(d)/(2*r)

if d%(2*r) !=0:
    steps +=1

print steps