import math

def distance(a, b):
    m = len(a)
    c = 0
    for i in range(m):
        c += (a[i] - b[i]) ** 2
    return c ** 0.5


def solve(a, b, r):
    return math.ceil(distance(a, b) / (2 * r))


r, x0, y0, x1, y1 = [int(s) for s in input().split(' ')]


print(solve((x0, y0), (x1, y1), r))


