using System;

class Program
{
    static void Main()
    {
        int n = int.Parse(Console.ReadLine());
        long[] c = new long[n];
        long[] d = new long[n];
        for (int i = 0; i < n; i++)
        {
            string[] s = Console.ReadLine().Split();
            c[i] = long.Parse(s[0]);
            d[i] = long.Parse(s[1]);
        }

        long sum = 0;

        for (int i = 0; i < n; i++)
        {
            int t = 1000000007;

            if (c[i] % 2 == 0) sum += ((c[i] / 2) % t) * (d[i] % t);
            else sum += (((c[i] + 1) / 2) % t) * (d[i] % t);

            sum %= t;
        }

        Console.WriteLine(sum);
    }
}