#include<bits/stdc++.h>
//ios::sync_with_stdio(false);
//cin.tie(0);
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> pii;
typedef pair<pii,int> ppii;
typedef pair<int,pii> pipi;
typedef pair<ll,ll> pll;
typedef pair<pll,ll> ppll;
typedef pair<ll,pll> plpl;
typedef tuple<ll,ll,ll> tl;
ll mod=1000000007;
ll mod2=998244353;
ll mod3=1000003;
ll mod4=998244853;
ll inf=1000000000000000000;
double pi=2*acos(0);
#define rep(i,m,n) for(ll i=m;i<n;i++)
#define rrep(i,n,m) for(ll i=n;i>=m;i--)
int dh[4]={1,-1,0,0};
int dw[4]={0,0,1,-1};
int ddh[8]={-1,-1,-1,0,0,1,1,1};
int ddw[8]={-1,0,1,-1,1,-1,0,1};
ll lmax(ll a,ll b){
    if(a<b)return b;
    else return a;
}
ll lmin(ll a,ll b){
    if(a<b)return a;
    else return b;
}
ll gcd(ll a,ll b){
    if(a<b)swap(a,b);
    if(a%b==0)return b;
    return gcd(b,a%b);
}
ll Pow(ll n,ll k){
    ll ret=1;
    ll now=n;
    while(k>0){
        if(k&1)ret*=now;
        now*=now;
        k/=2;
    }
    return ret;
}
vector<vector<ll>> matmul(vector<vector<ll>> a,vector<vector<ll>> b){
    ll n=a.size();
    vector<vector<ll>> ret;
    vector<ll> e;
    rep(i,0,n)e.push_back(0);
    rep(i,0,n)ret.push_back(e);
    rep(i,0,n){
        rep(j,0,n){
            ll sum=0;
            rep(k,0,n){
                sum+=(a[i][k]*b[k][j])%mod;
                sum%=mod;
            }
            ret[i][j]=sum;
        }
    }
    return ret;
}
vector<vector<ll>> matbeki(vector<vector<ll>> a,ll n){
    vector<vector<ll>> ret;
    ll m=a.size();
    vector<ll> e;
    rep(i,0,m)e.push_back(0);
    rep(i,0,m)ret.push_back(e);
    rep(i,0,m){
        rep(j,0,m){
            if(i==j)ret[i][j]=1;
            else ret[i][j]=0;
        }
    }
    
    while(n>0){
        if(n%2){
            ret=matmul(ret,a);
            
        }
        a=matmul(a,a);
        n/=2;
    }
    return ret;
}
int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    ll a,b,n;cin>>a>>b>>n;
    vector<vector<ll>> v{{a,b,0},{1,0,0},{0,1,0}};
    if(n==0)cout<<0<<endl;
    else if(n==1)cout<<1<<endl;
    else if(n==2)cout<<a<<endl;
    else{
        v=matbeki(v,n-2);
        ll ans=a*v[0][0]+v[0][1];
        cout<<ans%mod<<endl;
    }
}