n=int(input())
xy=[]
for i in range(n):
    x,y=map(int,input().split())
    xy.append([x,y])

x0,y0=xy[0][0],xy[0][1]
ans=0
for i in range(1,n):
    xi,yi=xy[i][0],xy[i][1]
    dis=10**12
    for j in range(1,n):
        if j!=i:
            dis=min((xy[j][0]-xi)**2+(xy[j][1]-yi)**2,dis)
    if dis>(x0-xi)**2+(y0-yi)**2:
        ans+=1
        xy[i]=[10**11,10**11]
print(ans)