from sys import stdin,stdout
from collections import Counter
def ai(): return list(map(int, stdin.readline().split()))
def ei(): return map(int, stdin.readline().split())
def ip(): return  int(stdin.readline().strip())
def op(ans): return stdout.write(str(ans) + '\n')
from math import ceil
import math

r,x,y,a,b=ei()
d = math.sqrt((a-x)**2+(b-y)**2)
print(ceil(d/(2*r)))