import math
my_input = map(int,raw_input().split())

r = my_input[0]
x = my_input[1]
y = my_input[2]
a = my_input[3]
b = my_input[4]


total = math.sqrt(abs(a-x)**2 + abs(b-y)**2)

if total <= 0 :
    print 0
else :
    total -= 2*r
    total = int(math.ceil(total / float(r*2))) 
    print total +1
   

