package net.ipipip0129.yukicoder.no146;

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);

        int cnt = Integer.parseInt(scan.nextLine());

        long capacity = 0;

        for (int i = 0; i < cnt; i++) {
            String[] data = scan.nextLine().split(" ");

            capacity += ((Long.parseLong(data[0]) + 1) / 2 % 1000000007) * (Long.parseLong(data[1]) % 1000000007) % 1000000007;
        }

        System.out.println(capacity);
    }
}