from math import sqrt, pow, ceil
from decimal import *

#getcontext().prec = 10

#l1 = int(input())
l1 = input().split()
#l2 = input()
#l2 = input().split()

l1 = [int(i) for i in l1]
#l2 = [int(i) for i in l2]

#cin >> r >> x1 >> y1 >> x2 >> y2;
d = sqrt(pow(l1[3] - l1[1], 2) + pow(l1[4] - l1[2], 2));
print(ceil(d / l1[0] / 2));
  		  		   		  			  	 		   		 	