using System;

public class Hello
{
    public const int MOD = 1000000007;
    public static void Main()
    {
        var ans = 0L;
        var n = int.Parse(Console.ReadLine().Trim());
        for (int i = 0; i < n; i++)
        {
            string[] line = Console.ReadLine().Trim().Split(' ');
            var c = long.Parse(line[0]);
            var d = long.Parse(line[1]);
            if (c % 2 == 0) ans += c / 2 * d;
            else ans += (c + 1) / 2 * d;
            ans %= MOD;
        }
        Console.WriteLine(ans);
    }
}