inp = list(map(int,input().split()))
r=inp[0]
x1=inp[1]
y1=inp[2]
x2=inp[3]
y2=inp[4]
d=pow((x1-x2)**2+(y1-y2)**2,0.5)
d_in=int(d)
flag=1
if x1==x2 and y1==y2:
    print (0)
    flag=0
if d<=2*r and flag==1:
    print (1)
    flag=0
if  d==d_in and flag==1:
    if d_in%(2*r)==0:
        print (int((d_in-2*r)//(2*r))+1)
        flag=0
if flag==1:
    print (int((d-2*r)//(2*r))+2)