import java.io.*;
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int n = sc.nextInt();
        Baloon[] baloons = new Baloon[n];
        PriorityQueue<Distance> distances = new PriorityQueue<>();
        for (int i = 0; i < n; i++) {
            baloons[i] = new Baloon(sc.nextInt(), sc.nextInt());
            for (int j = 0; j < i; j++) {
                distances.add(new Distance(j, i, baloons[i].getDistance(baloons[j])));
            }
        }
        int count = 0;
        HashSet<Integer> displaced = new HashSet<>();
        while (distances.size() > 0) {
            Distance x = distances.poll();
            if (x.left == 0) {
                if (!displaced.contains(x.right)) {
                    count++;
                    displaced.add(x.right);
                }
            } else if (!displaced.contains(x.left) && !displaced.contains(x.right)) {
                displaced.add(x.left);
                displaced.add(x.right);
            }
        }
        System.out.println(count);
    }
    
    static class Distance implements Comparable<Distance> {
        int left;
        int right;
        long length;
        
        public Distance(int left, int right, long length) {
            this.left = left;
            this.right = right;
            this.length = length;
        }
        
        public int compareTo(Distance another) {
            if (length == another.length) {
                return 0;
            } else if (length < another.length) {
                return -1;
            } else {
                return 1;
            }
        }
    }
    
    static class Baloon {
        long x;
        long y;
        
        public Baloon(long x, long y) {
            this.x = x;
            this.y = y;
        }
        
        public long getDistance(Baloon another) {
            return (x - another.x) * (x - another.x) + (y - another.y) * (y - another.y);
        }
    }
}
    
class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    StringBuilder sb = new StringBuilder();
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public double nextDouble() throws Exception {
        return Double.parseDouble(next());
    }
    
    public String next() throws Exception {
        while (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
    
}