r, x1, y1, x2, y2 = map(int, input().split())

import math

def dist(p1, p2):
    x = p1[0]-p2[0]
    y = p1[1]-p2[1]
    return math.sqrt(x**2 + y**2)

print(math.ceil(dist((x1, y1), (x2, y2)) / (2*r)))