using System;
using System.Linq;

public class Program
{
	public static void Main()
	{
		long mod = (long)1e9 + 7;
		int N = int.Parse(Console.ReadLine());
		long ans = 0;
		for (int i = 0; i < N; i++)
		{
			var CD = Console.ReadLine().Split().Select(j => long.Parse(j)).ToArray();
			long C = CD[0], D = CD[1];
			C = (C + 1) / 2 % mod;
			D %= mod;
			ans += C * D;
			ans %= mod;
		}
		Console.WriteLine(ans);
	}
}