#include <iostream>
#include <iterator>
#include <ranges>
#include <vector>

// this is a solution for miniexcercise from lesson 04

int main() {
    std::vector<int> v;
    std::size_t n;

    while (std::cin >> n) {
        v.push_back(n);
    }

    // std::ranges::next(it, 2, v.rend()) is a way to advance iterator it by 2 positions in a safe way (it checks that we do not go past v.rend())
    for (auto it = v.rbegin(); it < v.rend(); it = std::ranges::next(it, 2, v.rend())) {
        (*it) *= 2;
    }

    for (auto it = v.cbegin(); it < v.cend(); it = std::ranges::next(it, 3, v.cend())) {
        std::cout << *it << ' ';
    }

    std::cout << std::endl;
}