using System;
using System.Linq;

class No146
{
    static void Main()
    {
        var count = Int64.Parse(Console.ReadLine());
        var mod = 1000000007;
        long ans = 0;
        for (long i = 0; i < count; ++i)
        {
            var chair = Console.ReadLine().Split(' ').Select(x => long.Parse(x)).ToArray();
            var p = ((chair[0]+1)/ 2)%mod;
            ans += p * chair[1];
            ans %= mod;
        }
        Console.WriteLine(ans);
    }
}