import java.io.IOException;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) throws IOException {
        Scanner sc = new Scanner(System.in);
        int N = Integer.parseInt(sc.next());
        long accomodates = 0;
        int mod = 1000000007;
        for (long i = 0; i < N; i++) {
            long c = sc.nextLong();
            long d = sc.nextLong();
            c = (c + 1) / 2;
            c = c % mod;
            d = d % mod;

            accomodates += (c * d);
            accomodates %= mod;
        }
        System.out.println(accomodates);
    }
}