from math import sqrt
r,x1,y1,x2,y2 = input().split()
r,x1,y1,x2,y2 = map(int,[r,x1,y1,x2,y2])
d = sqrt((x1-x2)**2+(y1-y2)**2)
if d/(2*r) == int(d/(2*r)):
    s = int(d/(2*r))
    print(s)
else:
    s = int(d/(2*r))
    print(s+1)