import math
def distance(x1, y1, x2, y2):
    return math.sqrt(pow(x1-x2, 2)+pow(y1-y2, 2))

r, x, y, xd, yd = map(int, input().split())
d = 2*r
dist = distance(x, y, xd, yd)
print(math.ceil(dist/d))
