from math import sqrt, ceil
params = list(map(int,list(input().split())))
r, x1, y1, x2, y2 = params[0], params[1], params[2], params[3], params[4]

delta = sqrt((abs(x1 - x2)**2 + abs(y1-y2)**2))

print(ceil(delta / (2*r)))
	 	 	 				 	 	 	 	    		 	 				