#include <bits/stdc++.h>
using namespace std;
const long long MOD = 1000000007;
vector<vector<long long>> matmul(vector<vector<long long>> A, vector<vector<long long>> B){
	int N = A.size();
	vector<vector<long long>> ans(N, vector<long long>(N, 0));
	for (int i = 0; i < N; i++){
		for (int j = 0; j < N; j++){
			for (int k = 0; k < N; k++){
				ans[i][k] += A[i][j] * B[j][k];
				ans[i][k] %= MOD;
			}
		}
	}
	return ans;
}
vector<vector<long long>> matexp(vector<vector<long long>> A, long long b){
	int N = A.size();
	vector<vector<long long>> ans(N, vector<long long>(N, 0));
	for (int i = 0; i < N; i++){
		ans[i][i] = 1;
	}
	while (b > 0){
		if (b % 2 == 1){
			ans = matmul(ans, A);
		}
		A = matmul(A, A);
		b /= 2;
	}
	return ans;
}
int main(){
  long long a, b;
  cin >> a >> b;
  long long n;
  cin >> n;
  vector<vector<long long>> mat = {{a * 2 % MOD, (b - a * a % MOD + MOD) % MOD}, {1, 0}};
  mat = matexp(mat, n);
  long long ans = (mat[1][0] * a * 2 + mat[1][1] * 2) % MOD;
  cout << ans << endl;
}