from collections import *
from bisect import *
from math import *
from heapq import *
from fractions import *
import sys
input=sys.stdin.readline
t=1
def r(a):
    return ((a*(a-1))//2)
while(t):
    t-=1
    r,x,y,x1,y1=map(int,input().split())
    d=pow(abs(x-x1),2)+pow(abs(y-y1),2)
    d=pow(d,0.5)
    print(ceil(d/(2*r)))
