import java.util.Scanner;

public class N146 {

	public static void main(String[] args) {

		Scanner sca = new Scanner(System.in);

		int n = sca.nextInt();
		long A = 0;
		long mod = 100000007;

		for (int i = 0; i < n; i++) {
			Long C = sca.nextLong();
			Long D = sca.nextLong();

			if (C % 2 == 0) {
				long t = C / 2;
				t %= mod;
				D %= mod;
				A += t * D;
			} else {
				long t = C / 2 + 1;
				t %= mod;
				D %= mod;
				A += t * D;
			}
			A %= mod;
		}

		System.out.println(A);

	}

}