import math

def no_of_steps(r,xi,yi,xf,yf):
    distance = math.sqrt((xf-xi)**2+(yf-yi)**2)
    if distance%(2*r) == 0:
        return int(distance)//(2*r)
    else:
        return (int(distance)//(2*r)) + 1

data = list(map(int, input().split()))
r = data[0]
(xi,yi) = (data[1],data[2])
(xf,yf) = (data[3],data[4])
print(no_of_steps(r,xi,yi,xf,yf))