#[doc = " https://github.com/hatoo/competitive-rust-snippets"]
#[allow(unused_imports)]
use std::cmp::{max, min, Ordering};
#[allow(unused_imports)]
use std::collections::{BTreeMap, BTreeSet, BinaryHeap, HashMap, HashSet, VecDeque};
#[allow(unused_imports)]
use std::io::{stdin, stdout, BufWriter, Write};
#[allow(unused_imports)]
use std::iter::FromIterator;
#[allow(unused_macros)]
macro_rules ! debug { ( $ ( $ a : expr ) ,* ) => { eprintln ! ( concat ! ( $ ( stringify ! ( $ a ) , " = {:?}, " ) ,* ) , $ ( $ a ) ,* ) ; } }
#[macro_export]
macro_rules ! input { ( source = $ s : expr , $ ( $ r : tt ) * ) => { let mut parser = Parser :: from_str ( $ s ) ; input_inner ! { parser , $ ( $ r ) * } } ; ( parser = $ parser : ident , $ ( $ r : tt ) * ) => { input_inner ! { $ parser , $ ( $ r ) * } } ; ( new_stdin_parser = $ parser : ident , $ ( $ r : tt ) * ) => { let stdin = std :: io :: stdin ( ) ; let reader = std :: io :: BufReader :: new ( stdin . lock ( ) ) ; let mut $ parser = Parser :: new ( reader ) ; input_inner ! { $ parser , $ ( $ r ) * } } ; ( $ ( $ r : tt ) * ) => { input ! { new_stdin_parser = parser , $ ( $ r ) * } } ; }
#[macro_export]
macro_rules ! input_inner { ( $ parser : ident ) => { } ; ( $ parser : ident , ) => { } ; ( $ parser : ident , $ var : ident : $ t : tt $ ( $ r : tt ) * ) => { let $ var = read_value ! ( $ parser , $ t ) ; input_inner ! { $ parser $ ( $ r ) * } } ; }
#[macro_export]
macro_rules ! read_value { ( $ parser : ident , ( $ ( $ t : tt ) ,* ) ) => { ( $ ( read_value ! ( $ parser , $ t ) ) ,* ) } ; ( $ parser : ident , [ $ t : tt ; $ len : expr ] ) => { ( 0 ..$ len ) . map ( | _ | read_value ! ( $ parser , $ t ) ) . collect ::< Vec < _ >> ( ) } ; ( $ parser : ident , chars ) => { read_value ! ( $ parser , String ) . chars ( ) . collect ::< Vec < char >> ( ) } ; ( $ parser : ident , usize1 ) => { read_value ! ( $ parser , usize ) - 1 } ; ( $ parser : ident , $ t : ty ) => { $ parser . next ::<$ t > ( ) . expect ( "Parse error" ) } ; }
use std::io;
use std::io::BufRead;
use std::str;
pub struct Parser<R> {
    reader: R,
    buf: Vec<u8>,
    pos: usize,
}
impl Parser<io::Empty> {
    pub fn from_str(s: &str) -> Parser<io::Empty> {
        Parser {
            reader: io::empty(),
            buf: s.as_bytes().to_vec(),
            pos: 0,
        }
    }
}
impl<R: BufRead> Parser<R> {
    pub fn new(reader: R) -> Parser<R> {
        Parser {
            reader: reader,
            buf: vec![],
            pos: 0,
        }
    }
    pub fn update_buf(&mut self) {
        self.buf.clear();
        self.pos = 0;
        loop {
            let (len, complete) = {
                let buf2 = self.reader.fill_buf().unwrap();
                self.buf.extend_from_slice(buf2);
                let len = buf2.len();
                if len == 0 {
                    break;
                }
                (len, buf2[len - 1] <= 0x20)
            };
            self.reader.consume(len);
            if complete {
                break;
            }
        }
    }
    pub fn next<T: str::FromStr>(&mut self) -> Result<T, T::Err> {
        loop {
            let mut begin = self.pos;
            while begin < self.buf.len() && (self.buf[begin] <= 0x20) {
                begin += 1;
            }
            let mut end = begin;
            while end < self.buf.len() && (self.buf[end] > 0x20) {
                end += 1;
            }
            if begin != self.buf.len() {
                self.pos = end;
                return str::from_utf8(&self.buf[begin..end]).unwrap().parse::<T>();
            } else {
                self.update_buf();
            }
        }
    }
}
#[allow(unused_macros)]
macro_rules ! debug { ( $ ( $ a : expr ) ,* ) => { eprintln ! ( concat ! ( $ ( stringify ! ( $ a ) , " = {:?}, " ) ,* ) , $ ( $ a ) ,* ) ; } }
#[doc = " https://github.com/hatoo/competitive-rust-snippets"]
const BIG_STACK_SIZE: bool = true;
#[allow(dead_code)]
fn main() {
    use std::thread;
    if BIG_STACK_SIZE {
        thread::Builder::new()
            .stack_size(32 * 1024 * 1024)
            .name("solve".into())
            .spawn(solve)
            .unwrap()
            .join()
            .unwrap();
    } else {
        solve();
    }
}
fn mat_mul(x: &[Vec<i64>], y: &[Vec<i64>], mo: i64) -> Vec<Vec<i64>> {
    vec![
        vec![(x[0][0]*y[0][0]+x[0][1]*y[1][0]) % mo, (x[0][0]*y[0][1]+x[0][1]*y[1][1]) % mo],
        vec![(x[1][0]*y[0][0]+x[1][1]*y[1][0]) % mo, (x[1][0]*y[0][1]+x[1][1]*y[1][1]) % mo]
    ]
}
fn mat_add(x: &[Vec<i64>], y: &[Vec<i64>], mo: i64) -> Vec<Vec<i64>> {
    vec![
        vec![(x[0][0]+y[0][0]) % mo, (x[0][1]+y[0][1]) % mo],
        vec![(x[0][1]+y[0][1]) % mo, (x[1][1]+y[1][1]) % mo],
    ]
}
fn mat_apply(x: &[Vec<i64>], y: &[i64], mo: i64) -> Vec<i64> {
    vec![
        (x[0][0]*y[0]+x[0][1]*y[1]) % mo,
        (x[1][0]*y[0]+x[1][1]*y[1]) % mo
    ]
}
fn solve() {
    input!{
        a:i64,b:i64,n:usize,
    }
    let mo = 1_000_000_007;
    if n==0 {
        println!("0");
        return
    }
    if n==1 {
        println!("1");
        return
    }

    let bd = bin_digits(n-1);
    let mut muls = vec![];
    let mut acc = vec![
        vec![a, b],
        vec![1, 0],
    ];
    muls.push(acc.clone());
    for i in 0..60 {
        acc = mat_mul(&acc, &acc, mo);
        muls.push(acc.clone());
    }
    
    let mut acc = vec![
        vec![1,0],
        vec![0,1],
    ];
    for i in 0..bd.len() {
        if bd[i] {
            acc = mat_mul(&acc, &muls[i], mo);
        }
    }
    let res = mat_apply(&acc, &vec![1,0], mo);
    println!("{}",res[0]);
}
fn bin_digits(n: usize) -> Vec<bool> {
    if n == 0 {
        return vec![];
    }
    let logN = (n as f64).log2().floor() as usize;
    let mut res = vec![false; logN + 1];
    let mut n = n;
    for k in (0..logN + 1).rev() {
        if n >= 1 << k {
            res[k] = true;
            n -= (1 << k);
        }
    }
    res
}