import java.util.Scanner;

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

		long sum = 0;
		for(int i = 0; i < N; i++) {
			long C = scan.nextLong();
			long D = scan.nextLong();
			long k;
			if(C% 2 == 0) {
				k =  C / 2;
				k = k % (1000000007);
			}else {
				k = C / 2 + 1;
				k = k % (1000000007);
			}
			sum += (k * D) % (1000000007);
		}
		scan.close();

		long ans = sum % (1000000007);
		System.out.println(ans);
	}
}