#include <cstdio>
#include <cstring>
using namespace std;
struct mat
{
    int d[2][2];
    const mat &operator=(const mat &rhs)
    {
        memcpy(this, &rhs, sizeof(rhs));
        return *this;
    }
    const mat &operator*=(const mat &rhs)
    {
        mat ret;
        memset(&ret, 0, sizeof(ret));
        for (int i = 0; i < 2; i++)
            for (int j = 0; j < 2; j++)
                for (int k = 0; k < 2; k++)
                    ret.d[i][j] += d[i][k] * rhs.d[k][j], ret.d[i][j] %= 7;
        memcpy(this, &ret, sizeof(ret));
        return *this;
    }
};
template <typename T>
void fpow(T &ans, const T &a, int b)
{
    for (T x = a; b; b >>= 1)
    {
        if (b & 1)
            ans *= x;
        x *= x;
    }
}
int main()
{
    int a, b, n;
    while (scanf("%d%d%d", &a, &b, &n), a | b | n)
        if (n <= 2)
            puts("1");
        else
        {
            mat ans, mul;
            ans.d[0][0] = ans.d[1][1] = 1;
            ans.d[0][1] = ans.d[1][0] = 0;
            mul.d[0][0] = a;
            mul.d[0][1] = b;
            mul.d[1][0] = 1;
            mul.d[1][1] = 0;
            fpow(ans, mul, n - 2);
            printf("%d\n", (ans.d[0][0] + ans.d[0][1]) % 7);
        }
    return 0;
}