Parallel LowerBound

// <execution>
// EXECUTION POLICIES
namespace execution {
    class sequenced_policy {
        // indicates support for only sequential execution, and requests termination on exceptions
    public:
        using _Standard_execution_policy   = int;
        static constexpr bool _Parallelize = false;
        static constexpr bool _Ivdep       = false;
    };

    inline constexpr sequenced_policy seq{/* unspecified */};

    class parallel_policy {
        // indicates support by element access functions for parallel execution with parallel forward progress
        // guarantees, and requests termination on exceptions
    public:
        using _Standard_execution_policy   = int;
        static constexpr bool _Parallelize = true;
        static constexpr bool _Ivdep       = true;
    };

    inline constexpr parallel_policy par{/* unspecified */};

    class parallel_unsequenced_policy {
        // indicates support by element access functions for parallel execution with weakly parallel forward progress
        // guarantees, and requests termination on exceptions
        //
        // (at this time, equivalent to parallel_policy)
    public:
        using _Standard_execution_policy   = int;
        static constexpr bool _Parallelize = true;
        static constexpr bool _Ivdep       = true;
    };

    inline constexpr parallel_unsequenced_policy par_unseq{/* unspecified */};
/* ... */

}

// main.cpp https://praktikum.yandex.ru/trainer/cpp/lesson/967eacdd-7320-4832-8f65-57ff96ec2d5a/task/e9f59bfc-56e9-4cf8-aed2-92010996a7fd/?hideTheory=1

template <typename RandomAccessIterator, typename Value>
RandomAccessIterator LowerBound(const execution::sequenced_policy&, RandomAccessIterator range_begin, RandomAccessIterator range_end, const Value& value) { ... }

template <typename RandomAccessIterator, typename Value>
RandomAccessIterator LowerBound(RandomAccessIterator range_begin, RandomAccessIterator range_end, const Value& value) { ... }

template <typename RandomAccessIterator, typename Value>
RandomAccessIterator LowerBound(const execution::parallel_policy&, RandomAccessIterator range_begin, RandomAccessIterator range_end, const Value& value) { ... }

// https://en.cppreference.com/w/cpp/algorithm/transform

template< class ExecutionPolicy, class ForwardIt1, class ForwardIt2, class UnaryOperation >
ForwardIt2 transform( ExecutionPolicy&& policy, ForwardIt1 first1, ForwardIt1 last1,
                    ForwardIt2 d_first, UnaryOperation unary_op );