from math import sqrt
from math import ceil

splitted = [int(amit) for amit in raw_input().split(" ")]

r = splitted[0]

x1 = splitted[1]
y1 = splitted[2]
x2 = splitted[3]
y2 = splitted[4]

dist = sqrt(((x2 - x1)**2) + ((y2 - y1)**2))

print int((ceil(dist/(2*r))))