import java.util.*;

public class Run {
    final static int M = 1000000007;
    public static void main (String arg[]) {
        Scanner scan = new Scanner(System.in);
        int N = scan.nextInt();
        long C, D, ans = 0;
        for (int i = 0; i < N; i++) {
            C = scan.nextLong();
            C = (C + 1)/2;
            C %= M;
            D = scan.nextLong() % M;
            ans = (ans + C * D) % M;
        }
        System.out.println(ans);
    }
}