#include <iostream>
#include <vector>

int main() {
    const std::vector<int> source{3, 1, 4, 1, 5};
    auto first = source.begin() + 1;
    auto last = source.begin() + 4;
    std::vector<int> middle(first, last);
    std::cout << middle.size() << ' ' << middle[0] << ' '
              << middle[1] << ' ' << middle[2] << '\n';
    middle[0] += 10;
    std::cout << source[1] << ' ' << middle[0] << '\n';

    const std::vector<int> empty(first, first);
    std::cout << empty.size() << '\n';
    return 0;
}