r, x, y, z, w = [int(r) for r in input().split()]

def steps(r,x,y,z,w):
  diameter=2*r
  d=pow(((x-z)**2+(y-w)**2),0.5)
  if d%diameter==0:
      stepreq=d//diameter
  else:
      stepreq=1+d//diameter
  print(int(stepreq))
  
steps(r,x,y,z,w)