import math

ls = input().split(" ")
r = int(ls[0])
x1 = int(ls[1])
y1 = int(ls[2])
x2 = int(ls[3])
y2 = int(ls[4])

x_abs = abs(x1 - x2)
y_abs = abs(y1 - y2)
m = math.sqrt((x_abs * x_abs) + (y_abs * y_abs))

if m == 0:
    print(0)
elif m <= (2 * r):
    print(1)
else:
    print(math.ceil(m / (2 * r)))
