1
n = int(input())
2
p = []
3
for i in range(n):
4
    x, y = map(int, input().split())
5
    p.append((x, y))
6
    
7
ans = 0    
8
 
9
for i in range(n):
10
    up = False
11
    for j in range(n):
12
        if i != j and p[i][0] == p[j][0] and p[i][1] < p[j][1]:
13
            up = True
14
            break
15
    bottom = False
16
    for j in range(n):
17
        if i != j and p[i][0] == p[j][0] and p[i][1] > p[j][1]:
18
            bottom = True
19
            break
20
    left = False
21
    for j in range(n):
22
        if i != j and p[i][0] > p[j][0] and p[i][1] == p[j][1]:
23
            left = True
24
            break
25
    right = False
26
    for j in range(n):
27
        if i != j and p[i][0] < p[j][0] and p[i][1] == p[j][1]:
28
            right = True
29
            break
30
    
31
    if up == True and bottom == True and left == True and right == True:
32
        ans += 1
33
        
34
print(ans)