import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    public static void main(String[] args) {
        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */      double a,b,t,virus=1;
        
        Scanner scan = new Scanner(System.in);
        a = scan.nextDouble();
        b = scan.nextDouble();
        t = scan.nextDouble();
        for(float i=1;i<=t;i++){
            virus = a*virus*0.5 + b*virus*0.5;
        }
        virus = virus%(java.lang.Math.pow(10,9)+7);
        System.out.println((int)virus);
    }
}