import java.util.Scanner;

public class Main {
	public static void main(String[] args) throws Exception {
		Scanner koko = new Scanner(System.in);
		int n = Integer.parseInt(koko.nextLine());

		long total = 0;
		for (int i = 0; i < n; i++) {
			String[] input = koko.nextLine().split(" ");
			long c = Long.parseLong(input[0]);
			long d = Long.parseLong(input[1]);
			d = d % 1000000007;

			if (c % 2 == 0) {
				long e = c / 2;
				e = e % 1000000007;
				long t = e * d;
				t = t % 1000000007;
				total = total + t;
			} else {
				long e = (c + 1) / 2;
				e = e % 1000000007;
				long t = e * d;

				t = t % 1000000007;
				total = total + t;
			}

			total = total % 1000000007;
		}
		System.out.println(total);
	}
}