import math

a = raw_input()
a = a.split()

a = map(int, a)

r = a[0]
x = a[1]
y = a[2]
xnew = a[3]
ynew = a[4]

dist = math.sqrt((xnew - x)*(xnew - x) + (ynew - y)*(ynew - y))

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