#!/usr/bin/env python
#-*- coding:utf-8 -*-

import sys
import math
import random
import operator
from fractions import Fraction, gcd
from decimal import Decimal, getcontext
from itertools import product, permutations, combinations
getcontext().prec = 100

MOD = 10**9 + 7
INF = float("+inf")

r, x, y, x2, y2 = map(int, raw_input().split())
EPS = 0.1 ** 15
dx = x2 - x
dy = y2 - y
dist = math.sqrt(dx ** 2 + dy ** 2)
k = math.ceil((dist) / (2 * r))
print int(k)



