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)

if q==0: print(0)
else: print(int(q/(2*r))+1)

  		 	   				   	          				