#yukicoder393F

'''
aftercontest これ解けそう
N^2 * logN が間に合うだろ
'''
from fractions import Fraction as Fc
from collections import defaultdict as dd
f=lambda:tuple(map(int,input().split()))

#直線の切片のx座標y座標を返す
def line(P,Q):
    x1,y1=P; x2,y2=Q
    if x1==x2: return (x1,10**100)
    R=Fc(y2-y1,x2-x1); return (R,-R*x1+y1)

N=int(input()); P=[f() for _ in range(N)]; ans=0

#各人に対して直線の式を計算する
for i in range(N):
    D=dd(list); hantei=0
    for j in range(N):
        if i==j: continue
        #高速化のため、関数化していた部分を解く
        x1,y1=P[i]; x2,y2=P[j]
        if x1==x2: D[(x1,10**100)].append(j)
        else:
            R=Fc(y2-y1,x2-x1); D[(R,-R*x1+y1)].append(j)
    for k in D:
        if len(D[k])==1: continue
        if k[1]==10**100:
            plus,minus=0,0
            for now in D[k]:
                if   P[i][1]<P[now][1] and not plus: plus=1
                elif P[i][1]>P[now][1] and not minus: minus=1
                else: hantei=1; break
        else:
            plus,minus=0,0
            for now in D[k]:
                if   P[i][0]<P[now][0] and not plus: plus=1
                elif P[i][0]>P[now][0] and not minus: minus=1
                else: hantei=1; break
    ans+=hantei
print(ans)