import math

r, x, y, xp, yp = map(float, raw_input().split(" "))
def dist(x1, y1, x2, y2):
    return math.sqrt((x1-x2)**2.0 + (y1 - y2)**2.0)

distance = dist(x, y, xp, yp)
steps = int(distance/(2.0*float(r)))
if abs(float(steps)*2.0*float(r) - distance) > 0.000001:
    steps = steps + 1

print steps