# You lost the game.
r,x1,y1,x2,y2 = map(int, input().split())
from math import *
dc = sqrt((y2-y1)**2 + (x2-x1)**2)
if round(dc,0) == dc and int(dc) % (2*r) == 0:
    print(int(dc) // (2*r))
else:
    print(floor(dc) // (2*r) + 1)
