#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    int a = 0, b = 0, t = 0;
    int cells = 1;
    double prob = 0.5;
    std::cin >> a >> b >> t;
    while( t > 0 ){
        cells += prob*a*cells + prob*b*cells;
        t--;
    }
    std::cout << cells-1 % 1000000007;
    return 0;
}