import math 
def distance(x1 , y1 , x2 , y2): 
    return math.sqrt(math.pow(x2 - x1, 2) +math.pow(y2 - y1, 2) ) 
  
r,x,y,x1,y1=map(int,input().split())
if(x1==x and y1==y):
    print(0)
else:
    d=distance(x,y,x1,y1)
    print(math.ceil(d/(2*r)))
   