package main

import (
	"fmt"
)

func main() {
	var n int
	if _, err := fmt.Scan(&n); err != nil {
		return
	}

	type Point struct {
		x, y int
	}

	points := make([]Point, n)
	for i := 0; i < n; i++ {
		fmt.Scan(&points[i].x, &points[i].y)
	}

	supercentralCount := 0

	for i := 0; i < n; i++ {
		hasRight, hasLeft, hasUpper, hasLower := false, false, false, false
		for j := 0; j < n; j++ {
			if points[j].x > points[i].x && points[j].y == points[i].y {
				hasRight = true
			}
			if points[j].x < points[i].x && points[j].y == points[i].y {
				hasLeft = true
			}
			if points[j].x == points[i].x && points[j].y > points[i].y {
				hasUpper = true
			}
			if points[j].x == points[i].x && points[j].y < points[i].y {
				hasLower = true
			}
		}
		if hasRight && hasLeft && hasUpper && hasLower {
			supercentralCount++
		}
	}

	fmt.Println(supercentralCount)
}