import math
def dist(x,y,x1,y1):
    return ( (x-x1)**2 + (y-y1)**2 )**(0.5)

r,x,y,xz,yz = [int(i) for i in input().split()]

q = dist(x,y,xz,yz)

print(math.ceil(q/(2*r)))

   	  		      		   	    	 		  	