from math import sqrt, ceil

s = input().split(" ")
s = map(int, s)
s = list(s)

r = s[0]
x = s[1]
y = s[2]
x1 = s[3]
y1 = s[4]

del s

dist = sqrt((x-x1)**2 + (y-y1)**2)
d = 2*r

resp = ceil(dist/d)
print(resp)
