import bisect
from collections import defaultdict
from collections import deque
import math
import re
import sys

def ni():
    return int(raw_input())

def nis():
    return map(int, raw_input().split())

def si():
    return raw_input()

def sis():
    return raw_input().split()

def spaced(a):
    return ' '.join(map(str, a))

r, x, y, xp, yp = nis()

hypot = math.sqrt(abs(x - xp) ** 2 + abs(y - yp) ** 2)

print int(math.ceil(hypot / (2 * r)))