template <typename T>
void hash_combine(std::size_t& seed, const T& v)
{
    std::hash<T> hasher;
    seed ^= hasher(v) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
}

namespace std
{

    template<>
    struct hash<KeyType>
    {
        size_t operator() (const KeyType& kt)
        {
            size_t seed = 0;
            hash_combine(seed, kt.x);
            hash_combine(seed, kt.y);
            hash_combine(seed, kt.z);
            return seed;
        }
    };
}