#include <iostream>
#include <array>
using namespace std;
constexpr int N = 1e1;
constexpr int f(int x) { return x*2; }
typedef array<int, N> A;
template<int... i> struct F { static constexpr A f() { return A{{ ::f(i)... }}; } };
template<class A, class B> struct C {};
template<int... i, int... j> struct C<F<i...>, F<j...>> : F<i..., (sizeof...(i)+j)...> { using T = F<i..., (sizeof...(i)+j)...>; };
template<int n> struct S : C<typename S<n/2>::T, typename S<n-n/2>::T> {};
template<> struct S<1> : F<0> { using T = F<0>; };
constexpr auto X = S<N>::f();
int main() { cout << X[3] << endl; }

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