import java.util.Scanner;
public class No146 {

	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);
		int n = s.nextInt();
		long tot = 0 , mod = (long)Math.pow(10, 9) + 7l;
		for(int i = 0;i < n;i++){
			long c = s.nextLong() , d = s.nextLong();
			long c2 = ((c + 1) / 2) % mod, d2 = d % mod;
			tot +=  (c2 * d2) % mod;
		}
		s.close();

		System.out.println(tot);

	}

}