using System;
using System.Collections.Generic;
using System.IO;
class Solution {
    static void Main(String[] args) {
        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution */
        var input = Console.ReadLine().Split(' ');
        var ar = Array.ConvertAll(input,long.Parse);
        
        var sum = (ar[0]*ar[2]*0.5)+(ar[1]*ar[2]*0.5);
        Console.WriteLine(sum %(Math.Pow(10,9)+7));
    }
}