1/* ***********************************************
  2Author :111qqz
  3Created Time :2017年10月01日 星期日 03时01分38秒
  4File Name :10655.cpp
  5************************************************ */
  6
  7#include <cstdio>
  8#include <cstring>
  9#include <iostream>
 10#include <algorithm>
 11#include <vector>
 12#include <queue>
 13#include <set>
 14#include <map>
 15#include <string>
 16#include <cmath>
 17#include <cstdlib>
 18#include <ctime>
 19#define PB push_back
 20#define fst first
 21#define sec second
 22#define lson l,m,rt<<1
 23#define rson m+1,r,rt<<1|1
 24#define ms(a,x) memset(a,x,sizeof(a))
 25typedef long long LL;
 26#define pi pair < int ,int >
 27#define MP make_pair
 28
 29using namespace std;
 30const double eps = 1E-8;
 31const int dx4[4]={1,0,0,-1};
 32const int dy4[4]={0,-1,1,0};
 33const int inf = 0x3f3f3f3f;
 34LL p,q,n;
 35struct Mat
 36{
 37    LL mat[105][105];
 38    void clear()
 39    {
 40    ms(mat,0);
 41    }
 42}M,M1;
 43Mat operator * (Mat a,Mat b)
 44{
 45    Mat c;
 46    c.clear();
 47    for ( int i = 0 ; i < 2 ; i++)
 48    for ( int j = 0 ; j < 2 ; j++)
 49        for ( int k = 0 ; k < 2 ; k++)
 50        c.mat[i][j] += a.mat[i][k] * b.mat[k][j];
 51    return c;
 52}
 53Mat operator ^ (Mat a,LL b)
 54{
 55    Mat ret;
 56    ret.clear();
 57    for ( int i = 0 ; i < 2 ; i++) ret.mat[i][i] = 1LL;
 58
 59    while (b>0)
 60    {
 61    if (b&1) ret = ret * a;
 62    a = a * a;
 63    b = b >> 1LL;
 64    }
 65    return ret;
 66}
 67LL solve()
 68{
 69    if (n==0) return 2LL;
 70    if (n==1) return p;
 71    if (n==2) return p*p-2*q;
 72    M1.clear();
 73    M1.mat[0][0] = p;
 74    M1.mat[1][0] = p*p-2*q;
 75    M.clear();
 76    M.mat[0][1] = 1;
 77    M.mat[1][0] = -q;
 78    M.mat[1][1] = p;
 79    Mat ans;
 80    ans.clear();
 81    ans = (M^(n-2))*M1;
 82    return ans.mat[1][0];
 83}
 84int main()
 85{
 86    #ifndef  ONLINE_JUDGE 
 87//  freopen("./in.txt","r",stdin);
 88  #endif
 89    while (scanf("%lld%lld%lld",&p,&q,&n)==3)
 90    {
 91        //if (p==0&&q==0) break;
 92        //scanf("%lld",&n);
 93        LL ans = solve();
 94        printf("%lld\n",ans);
 95    }
 96
 97  #ifndef ONLINE_JUDGE  
 98  fclose(stdin);
 99  #endif
100    return 0;
101}