from math import sqrt

r, x, y, x_line, y_line = map(int, input().split())

movement = 2*r

distance = (x - x_line)**2 + (y - y_line)**2
distance = sqrt(distance)

ans = distance / movement
if ans % 1 > 0:
    ans = ans / 1
    ans += 1
print(int(ans))
			 	 			 	 		 		 	  				     	