#import itertools, math
from collections import *
from fractions import *
from itertools import combinations, permutations, product
from math import ceil, exp, log, sqrt
from Queue import *

#n = input()
#a = [input()for _ in xrange(n)]
r, x, y, x1, y1 = map(int, raw_input().split())
#a = [map(int,raw_input().split())for _ in xrange(n)]
#s = raw_input()
#a = [raw_input() for _ in xrange(n)]
d = sqrt((x-x1)**2+(y-y1)**2)
#print d
print int(ceil(d / (2 * r)))