

#(amr and pins)


import math

# input
a,b,c,d,e = input().split()

r = int(a);
x1 = int(b); y1 = int(c);
x2 = int(d); y2 = int(e);

# (x1,y1) -> (x2,y2) distance between the centers
d = math.sqrt((x2-x1)**2 + (y2-y1)**2)

if d!=0:
    print(math.ceil(d/(2*r)))
    
if d ==0:
    print(0)
