from math import sqrt,ceil
r, x, y, x1, y1 = map(int, input().split())
if x == x1 and y1 == y:
    print(0)
    exit()
s = sqrt((x1 - x)**2 + (y1 - y)**2)
if s == 2*r:
    print(1)
if s < 2*r:
    print(1)
if s > 2 * r:
    print(ceil(s / (2 * r)))