# pylint: disable=unused-variable
# pylint: enable=too-many-lines
#* Just believe in yourself


#@ Author @CAP

import os
import sys
from io import BytesIO, IOBase
import math as M
import itertools as ITR
from collections import defaultdict as D
from collections import Counter as C
from collections import deque as Q
import threading
from functools import lru_cache, reduce
from functools import cmp_to_key as CMP
from bisect import bisect_left as BL
from bisect import bisect_right as BR
import random as R
import string
import cmath,time
enum=enumerate
start_time = time.time()

#? Variables

MOD=1_00_00_00_007; MA=float("inf"); MI=float("-inf")


#? Stack increment


def increase_stack():
    sys.setrecursionlimit(2**32//2-1)
    threading.stack_size(1 << 27)
    #sys.setrecursionlimit(10**6)
    #threading.stack_size(10**8)
    t = threading.Thread(target=main)
    t.start()
    t.join()


#? Region Funtions

def prints(a):
    print(a,end=" ")

def binary(n):
    return bin(n)[2:]


def decimal(s):
    return (int(s, 2))


def pow2(n):
    p = 0
    while (n > 1):
        n //= 2
        p += 1
    return (p)

def maxfactor(n):
    q = []
    for i in range(1,int(n ** 0.5) + 1):
        if n % i == 0: q.append(i)
    if q:
        return q[-1]


def factors(n):
    q = []
    for i in range(1,int(n ** 0.5) + 1):
        if n % i == 0: q.append(i); q.append(n // i)
    return(list(sorted(list(set(q)))))

def primeFactors(n):
    l=[]
    while n % 2 == 0:
        l.append(2)
        n = n / 2
    for i in range(3, int(M.sqrt(n)) + 1, 2):
        while n % i == 0:
            l.append(i)
            n = n / i
    if n > 2:
        l.append(int(n))
    l.sort()
    return (l)


def isPrime(n):
    if (n == 1):
        return (False)
    else:
        root = int(n ** 0.5)
        root += 1
        for i in range(2, root):
            if (n % i == 0):
                return (False)
        return (True)


def seive(n):
    a = [1]
    prime = [True for i in range(n + 1)] 
    p = 2
    while (p * p <= n): 
        if (prime[p] == True): 
            for i in range(p ** 2,n + 1,p): 
                prime[i] = False
        p = p + 1
    for p in range(2,n + 1): 
        if prime[p]: 
            a.append(p)
    return(a)


def maxPrimeFactors(n):
    maxPrime = -1
    while n % 2 == 0:
        maxPrime = 2
        n >>= 1
    for i in range(3, int(M.sqrt(n)) + 1, 2):
        while n % i == 0:
            maxPrime = i
            n = n / i
    if n > 2:
        maxPrime = n
    return int(maxPrime)


def countchar(s,i):
    c=0
    ch=s[i]
    for i in range(i,len(s)):
        if(s[i]==ch):
            c+=1
        else:
            break
    return(c)

def str_counter(a):
    q = [0] * 26
    for i in range(len(a)):
        q[ord(a[i]) - 97] = q[ord(a[i]) - 97] + 1
    return(q)

def lis(arr):
    n = len(arr)
    lis = [1] * n
    maximum=0

    for i in range(1, n):
        for j in range(0, i):
            if arr[i] > arr[j] and lis[i] < lis[j] + 1:
                lis[i] = lis[j] + 1
                maximum=max(maximum,lis[i])
    return maximum


def lcm(arr):
    a=arr[0]; val=arr[0]

    for i in range(1,len(arr)):

        gcd=gcd(a,arr[i])
        a=arr[i]; val*=arr[i]

    return val//gcd

def ncr(n,r):
    return M.factorial(n) // (M.factorial(n - r) * M.factorial(r))


def npr(n,r):
    return M.factorial(n) // M.factorial(n - r)


#? Region Taking Input

def inint():
    return int(inp())

def inarr():
    return list(map(int,inp().split()))

def invar():
    return map(int,inp().split())

def instr():
    s=inp()
    return list(s)

def insarr():
    return inp().split()
#? Region Fastio

BUFSIZE = 8192


class FastIO(IOBase):
    newlines = 0

    def __init__(self, file):
        self._fd = file.fileno()
        self.buffer = BytesIO()
        self.writable = "x" in file.mode or "r" not in file.mode
        self.write = self.buffer.write if self.writable else None

    def read(self):
        while True:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            if not b:
                break
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines = 0
        return self.buffer.read()

    def readline(self):
        while self.newlines == 0:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            self.newlines = b.count(b"\n") + (not b)
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines -= 1
        return self.buffer.readline()

    def flush(self):
        if self.writable:
            os.write(self._fd, self.buffer.getvalue())
            self.buffer.truncate(0), self.buffer.seek(0)


class IOWrapper(IOBase):
    def __init__(self, file):
        self.buffer = FastIO(file)
        self.flush = self.buffer.flush
        self.writable = self.buffer.writable
        self.write = lambda s: self.buffer.write(s.encode("ascii"))
        self.read = lambda: self.buffer.read().decode("ascii")
        self.readline = lambda: self.buffer.readline().decode("ascii")


sys.stdin, sys.stdout = IOWrapper(sys.stdin), IOWrapper(sys.stdout)
inp = lambda: sys.stdin.readline().rstrip("\r\n")


#<==================================== Write The Useful Code Here ============================

#< Make it one if there is some test cases
TestCases=0       #<=====================
#< =======================================
"""
> Sometimes later becomes never. Do it now.
! Be Better than yesterday.
* Your limitation—it’s only your imagination.
> Push yourself, because no one else is going to do it for you.
? The harder you work for something, the greater you’ll feel when you achieve it.
! Great things never come from comfort zones.
* Don’t stop when you’re tired. Stop when you’re done.
> Do something today that your future self will thank you for.
? It’s going to be hard, but hard does not mean impossible.
! Sometimes we’re tested not to show our weaknesses, but to discover our strengths.
"""
#@  Goal is to get Candidate Master
def solve():
    r,a,b,x,y=invar()
    dist=(x-a)**2+(y-b)**2
    dist=int(M.sqrt(dist))
    print(M.ceil(dist/(2*r)))




#! This is the Main Function

def main():
    flag=0
    #! Checking we are offline or not
    try:
        sys.stdin = open("c:/Users/Manoj Chowdary/Documents/python/CodeForces/contest-div-2/input.txt","r")
        sys.stdout = open("c:/Users/Manoj Chowdary/Documents/python/CodeForces/contest-div-2/output.txt","w")
    except: flag=1

    t=1
    if TestCases:
        t = inint()
    for _ in range(1,t + 1):
        solve()

    if not flag:
        print("Time: %.4f sec"%(time.time() - start_time))
        localtime = time.asctime( time.localtime(time.time()) )
        print(localtime)
        sys.stdout.close()



#? End Region


if __name__ == "__main__":

    #? Incresing Stack Limit
    #increase_stack()

    #! Calling Main Function
    main()