import math
r, x, y , x2, y2 = input().split()
r = int(r)
x = float(x)
y = float(y)
x2 = float(x2)
y2 = float(y2)

dist = math.sqrt(pow((x - x2), 2) + pow((y - y2), 2));

resp = int(dist / (2 * r));
comp = resp * r * 2
if comp != dist:
    resp +=1
    

print(resp)
				 		       			 			  	 						