#pragma once

#define EXERCISM_RUN_ALL_TESTS


#include <limits>
#include <stdexcept>


template <size_t   number_of_squares = 64,
          typename ulong_t = unsigned long long>
class custom_grains
{
    typedef typename std::numeric_limits<ulong_t> limits_t;

    static_assert(std::is_unsigned<ulong_t>::value,
            "ulong_t must be unsigned");

    static_assert(number_of_squares <= limits_t::digits,
            "ulong_t is too short");

    struct total_as_max
    {
        static inline ulong_t total()
        {
            return limits_t::max();
        }
    };

    struct total_by_shift
    {
        static inline ulong_t total()
        {
            return ulong_t(1) << number_of_squares - 1;
        }
    };

    typedef typename std::conditional<
        number_of_squares == limits_t::digits,
        total_as_max,
        total_by_shift>::type   total_policy_t;

public:

    static ulong_t square(size_t index)
    {
        if (index < 1 || index > number_of_squares)
            throw std::domain_error("invalid square number");

        return ulong_t(1) << (index - 1);
    }

    static ulong_t total()
    {
        return total_policy_t::total();
    }
};

typedef custom_grains<> grains;