r,x,y,x1,y1=map(int,input().split())
if x==x1 and y==y1:
    print(0)
else:
    dis=(x-x1)**2+(y-y1)**2
    dis=dis**(0.5)
    if dis/(2*r)==int(dis/(2*r)):
        print(int(dis/(2*r)))
    else:
        print(int(dis/(2*r)+1))


    
            
    
    
    


    
    

