import math

r, x1, y1, x2, y2 = [int(x) for x in input().split()]
c1 = (x1, y1)
c2 = (x2, y2)

def distance(a, b):
    xa, ya = a
    xb, yb = b

    return math.sqrt((xa - xb) ** 2 + (ya - yb) ** 2)

d = distance(c1, c2)
# print(f"Distance: {d}")
full_length_steps = int(d // (2*r))
if d - (2 * r * full_length_steps) == 0:
    print(full_length_steps)
else:
    print(full_length_steps + 1) # We need 1 steps to adjust to any point in between.

	    			 				  	 	  	    				 	