import sys
import math
from collections import Counter
from collections import OrderedDict
from collections import defaultdict
from functools import reduce
sys.setrecursionlimit(10**6)
def inputt():
    return sys.stdin.readline().strip()
def printt(n):
    sys.stdout.write(str(n)+'\n')
def listt():
    return [int(i) for i in inputt().split()]
 
def gcd(a,b): 
   return math.gcd(a,b) 
 
def lcm(a,b): 
    return (a*b) // gcd(a,b) 

def factors(n):
    step = 2 if n%2 else 1
    return set(reduce(list.__add__,([i, n//i] for i in range(1, int(math.sqrt(n))+1, step) if n % i == 0)))

def comb(n,k):
    factn=math.factorial(n)
    factk=math.factorial(k)
    fact=math.factorial(n-k)
    ans=factn//(factk*fact)
    return ans

def is_prime(n): 
    if n <= 1: 
        return False
    if n == 2: 
        return True
    if n > 2 and n % 2 == 0: 
        return False

    max_div = math.floor(math.sqrt(n)) 
    for i in range(3, 1 + max_div, 2): 
        if n % i == 0: 
            return False
    return True
def maxpower(n,x):
    B_max = int(math.log(n, x)) + 1#tells upto what power of x n is less than it like 1024->5^4
    return B_max

r,x1,y1,x2,y2=map(int,inputt().split())
d=0
d=(x2-x1)**2+(y2-y1)**2
d=d**(0.5)
print(math.ceil(d/(2*r)))