#include <iostream>
using namespace std;
typedef long long ll;

const ll mod = 1e9+7;

int main(void){
  ll a,b,n; cin >>a>>b>>n;
  if (n<=1) {cout<<n<<endl; return 0;}
  ll p[3]={0,1, -1};
  for(int i=2; i<=n; i++) {
    p[i%3] = (b*p[(i+1)%3] + a*p[(i+2)%3])%mod;
    //p[0]=p[1]; p[1]=p[2]; p[2]=(b*p[0]+a*p[1]) % mod;
  }
  
  cout<<p[n%3]<<endl;
}