r,x,y,x1,y1=list(map(int,input().split(" ")))



def amir(r,x,y,x1,y1): 
    d=((x1-x)**(2)+(y1-y)**(2))**(1/2)
    if d%(2*r)==0:
        print(int(d/(2*r)))
        return
    else:
        if d<2*r:
            print(1)
            return
        print(int(d//(2*r))+1)
        return
        
amir(r,x,y,x1,y1)