using System;
using System.Collections.Generic;
using System.IO;
class Solution {
    static void Main(String[] args) 
    {
        string[] arr_temp = Console.ReadLine().Split(' ');
        int[] arr = Array.ConvertAll(arr_temp,Int32.Parse);    
        int a = arr[0];
        int b = arr[1];
        int c = arr[2];
        
        var x = (.5 * a * c) + (.5 * b * c);
        int modRes = (int)(x % (Math.Pow(10,9) + 7));
        Console.WriteLine(modRes);
        
    }
}