package main

import (
	"fmt"
	"bufio"
	"os"
	"sort"
)

func main() {
	r := bufio.NewReader(os.Stdin)
	w := bufio.NewWriter(os.Stdout)
	defer w.Flush()
	var n int
	fmt.Fscan(r, &n)
	xy := make([][2]int, n)
	for i := 0; i < n; i++ {
		var x, y int
		fmt.Fscan(r, &x, &y)
		xy[i] = [2]int{x, y}
	}
	dist := make([][3]int, n * (n-1) / 2)
	k := 0
	for i := 0; i < n; i++ {
		xi, yi := xy[i][0], xy[i][1]
		for j := i+1; j < n; j++ {
			xj, yj := xy[j][0], xy[j][1]
			d := (xi - xj) * (xi - xj) + (yi - yj) * (yi - yj)
			dist[k] = [3]int{d, i, j}
			k++
		}
	}
	sort.Slice(dist, func(i, j int) bool {return dist[i][0] < dist[j][0]})
	dead := make([]bool, n)
	alive_n := n
	remove := 0
	for _, x := range dist {
		i, j := x[1], x[2]
		if i == 0 && !dead[j] {
			remove++
			dead[j] = true
			alive_n--
		} else if !dead[i] && !dead[j] {
			dead[i] = true
			dead[j] = true
		}
		if alive_n == 1 {
			break
		}
	}
	fmt.Fprintln(w, remove)
}