import java.util.Scanner;

public class Yuki146 {

    int MOD = 1000000007;


    public Yuki146() {
        Scanner scanner = new Scanner(System.in);
        int N = scanner.nextInt();
        //一行目の改行
        scanner.nextLine();
        long ans = 0;
        for (int i = 0; i < N; i++) {
            //通常のnextLongだと時間がかかる
            String[] d = scanner.nextLine().split(" ");
            long C = Long.parseLong(d[0]);
            long D = Long.parseLong(d[1]);

            C = (C + 1) / 2 % MOD;
            D = D % MOD;
            ans = ans + C * D;
            ans %= MOD;
        }
        System.out.println(ans);

    }

    public static void main(String[] args) {
        Yuki146 hoge = new Yuki146();
    }
}