#![allow(unused_imports)]
use std::cmp::*;
use std::collections::*;
use std::io::Write;
use std::ops::Bound::*;

#[allow(unused_macros)]
macro_rules! debug {
    ($($e:expr),*) => {
        #[cfg(debug_assertions)]
        $({
            let (e, mut err) = (stringify!($e), std::io::stderr());
            writeln!(err, "{} = {:?}", e, $e).unwrap()
        })*
    };
}

fn main() {
    let v = read_vec::<i64>();
    let (a, b) = (v[0], v[1]);
    let n = read::<u64>();
    if n == 0 {
        println!("{}", 2);
        return;
    }
    if n == 1 {
        println!("{}", (2 * a).rem_euclid(1000_000_007));
        return;
    }

    let mut c = mat_zeros(2, 2);
    c[0][0] = (2 * a).rem_euclid(1000_000_007);
    c[0][1] = (b - a * a).rem_euclid(1000_000_007);
    c[1][0] = 1;
    c[1][1] = 0;
    c = matpow(&c, n - 1);
    println!(
        "{}",
        ((c[0][0] * 2 * a) % 1000_000_007 + c[0][1] * 2) % (1000_000_007)
    );
}

type mat = Vec<Vec<i64>>;

fn mat_zeros(n: usize, m: usize) -> mat {
    vec![vec![0i64; m]; n]
}

fn matmul(a: &mat, b: &mat) -> mat {
    let mut c = mat_zeros(a.len(), b[0].len());
    for i in 0..a.len() {
        for k in 0..b.len() {
            for j in 0..b[0].len() {
                c[i][j] += (a[i][k] * b[k][j]) % 1000_000_007;
                c[i][j] %= 1000_000_007;
            }
        }
    }
    c
}

fn matpow(a: &mat, n: u64) -> mat {
    let mut b = mat_zeros(a.len(), a.len());
    for i in 0..a.len() {
        b[i][i] = 1;
    }
    let mut n = n;
    let mut a: mat = a.clone();
    while n > 0 {
        if n & 1 == 1 {
            b = matmul(&a, &b);
        }
        a = matmul(&a, &a);
        n >>= 1;
    }
    b
}

fn read<T: std::str::FromStr>() -> T {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    s.trim().parse().ok().unwrap()
}

fn read_vec<T: std::str::FromStr>() -> Vec<T> {
    read::<String>()
        .split_whitespace()
        .map(|e| e.parse().ok().unwrap())
        .collect()
}