Domino

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int upSum = 0, lowSum = 0;
        boolean hasOddPair = false;
        
        for (int i = 0; i < n; i++) {
            int x = sc.nextInt();
            int y = sc.nextInt();
            upSum += x;
            lowSum += y;
            if ((x + y) % 2 == 1) hasOddPair = true;
        }
        
        if (upSum % 2 == 0 && lowSum % 2 == 0) {
            System.out.println(0);
        } else if (upSum % 2 == 1 && lowSum % 2 == 1 && hasOddPair && n > 1) {
            System.out.println(1);
        } else {
            System.out.println(-1);
        }
        sc.close();
    }
}