#include<iostream>
#include<cstdio>
#include<cstring>
#define mem(a) memset(a,0,sizeof(a))
#define forn(i,n) for(int i=0;i<n;++i)
#define for1(i,n) for(int i=1;i<=n;++i)
#define IO std::ios::sync_with_stdio(false); std::cin.tie(0)
using namespace std;
typedef long long ll;
const int maxn=30;
const int mod=7;
const int inf=0x3f3f3f3f;

int n,m,k,t,x,y;
struct Matrix
{
    int val[2][2];
};

Matrix E=
{1,0,
 0,1
};

Matrix Multiply(Matrix a,Matrix b)
{
    Matrix ans=E;
    forn(i,2)
    forn(j,2)
    {
        int temp=0;
        forn(k,2)
        temp=(temp+a.val[i][k]*b.val[k][j]%mod)%mod;
        ans.val[i][j]=temp;
    }
    return ans;
}

int quick_pow(Matrix a,int n)
{
    Matrix res=E;
    while(n>0)
    {
        if(n&1)
        res=Multiply(res,a);
        a=Multiply(a,a);
        n>>=1;
    }
    int ans=0;
    ans=(res.val[0][0]+res.val[0][1])%mod;
    return ans;
}

int main(){
    IO;
    while(cin>>x>>y>>n)
    {
        if(x==y&&n==x&&x==0) break;
        Matrix t=
        {
            x,y,
            1,0
        };
        int ans=(quick_pow(t,n-2))%mod;
        cout<<ans<<endl;
    }
    return 0;
}