using System;
using System.Linq;

class Program
{
    static void Main(string[] args)
    {
        var n = int.Parse(Console.ReadLine());
        var sum = 0;
        for (int i = 0; i < n; i++)
        {
            var line = Console.ReadLine().Split(' ').Select(int.Parse).ToArray();
            int element = (line[0] + 1)/2;
            sum += element*line[1];
            sum %= 1000000000 + 7;
        }
        Console.WriteLine(sum);
    }
}