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

public class Main {

    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        int n = Integer.parseInt(br.readLine());

        int one, two, three, four, w;
        one = two = three = four = w = 0;
        while (n -- > 0) {
            String[] str = br.readLine().split(" ");
            int x = Integer.parseInt(str[0]), y = Integer.parseInt(str[1]);
            if (x > 0 && y > 0) one++;
            else if (x < 0 && y > 0) two++;
            else if (x < 0 && y < 0) three++;
            else four++;
        }

        int t1 = Math.min(one, three), t2 = Math.min(two, four);
        int t3 = Math.abs(one - three), t4 = Math.abs(two - four);
        w = 2 * (t1 + t2) + Math.min(t3, t4);
        System.out.println(w);
    }
}