import os

import math
import sys

debug = True

if debug and os.path.exists("input.in"):
    input = open("input.in", "r").readline
else:
    debug = False
    input = sys.stdin.readline


def inp():
    return (int(input()))


def inlt():
    return (list(map(int, input().split())))


def insr():
    s = input()
    return s[:len(s) - 1]  # Remove line char from end


def invr():
    return (map(int, input().split()))


test_count = 1
if debug:
    test_count = inp()

for t in range(test_count):
    if debug:
        print("Test Case #", t + 1)
    r, x1, y1, x2, y2 = invr()
    dist = math.sqrt((x1 - x2) ** 2 + (y1 - y2) ** 2)
    print(math.ceil(dist / (2 * r)))
