mod = 1000000007
ii = lambda : int(input())
si = lambda : input()
dgl = lambda : list(map(int, input()))
f = lambda : map(int, input().split())
il = lambda : list(map(int, input().split()))
ls = lambda : list(input())
from math import *
r,x,y,p,q=f()
print(ceil(((abs(p-x)**2+abs(q-y)**2)**0.5)/(2*r)))