using System;

public class Hello
{
    public static void Main()
    {
        var ans = 0L;
        var n = int.Parse(Console.ReadLine().Trim());
        for (int i = 0; i < n; i++)
        {
            var MOD = (long)Math.Pow(10, 9) + 7;
            string[] line = Console.ReadLine().Trim().Split(' ');
            var c = long.Parse(line[0]) % MOD;
            var d = long.Parse(line[1]) % MOD;
            var w = ((c + 1) / 2L) % MOD;
            w *= d; w %= MOD;
            ans += w;
            ans %= MOD;
        }
        Console.WriteLine(ans);
    }
}