#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define ALL(v) v.begin(), v.end()
typedef long long ll;

#include <bits/stdc++.h>
using namespace std;

#define MOD 1000000007

//m次正方行列の積
vector<vector<ll>> matrixmul(ll m,vector<vector<ll>> a,vector<vector<ll>> b){
  vector<vector<ll>> c(m,vector<ll>(m,0));
  rep(i,m){
    rep(j,m){
      rep(k,m) c[i][j]=(c[i][j]+a[i][k]*b[k][j]%MOD)%MOD;
    }
  }
  return c;
}

//m次正方行列vecのn乗
vector<vector<ll>> matrixpow(ll m,vector<vector<ll>> vec,ll n){
  vector<vector<ll>> ans(m,vector<ll>(m,0));
  rep(i,m) ans[i][i]=1;
  while(n){
    if(n&1) ans=matrixmul(m,ans,vec);
    vec=matrixmul(m,vec,vec);
    n>>=1;
  }
  return ans;
}

int main(){
  ll a,b,n;
  cin>>a>>b>>n;
  
  vector<vector<ll>> A(2,vector<ll> (2)),B(2,vector<ll> (2)),
  C(2,vector<ll> (2)),D(2,vector<ll> (2));
  A[0][0]=a,A[0][1]=b,A[1][0]=1LL,A[1][1]=a;
  B[0][0]=a,B[0][1]=-b,B[1][0]=-1LL,B[1][1]=a;
  C=matrixpow(2,A,n);
  D=matrixpow(2,B,n);
  cout<<(C[0][0]+D[0][0])%MOD<<endl;

  return 0;
}