r,x1,y1,x2,y2=input().split(" ")
r=int(r)
x1=int(x1)
y1=int(y1)
x2=int(x2)
y2=int(y2)
d=((x1-x2)**2+(y1-y2)**2)**0.5
d_int=int(d)
#print(d)
if d <= 2*r and d!=0 :
    print("1")
elif d==0 :
    print("0")
elif d>2*r and d_int==d :
    ans=d//(2*r)
    inte=d%(2*r)
    if inte!=0 :
        ans=ans+1
    print(ans)
elif d>2*r and d_int!=d :
    ans=d_int//(2*r)
    print(ans+1)


    
   






         
    


    







        

