#include <cassert>
#include <iostream>
#include <vector>

int main() {
    std::vector<int> values{10, 20};
    values.reserve(4);
    assert(values.size() == 2 && values.capacity() >= 4);
    int* first = &values.front();
    values.push_back(30);
    assert(*first == 10);
    assert(first == &values.front());

    values.resize(5);
    assert(values[3] == 0 && values[4] == 0);
    values.resize(3);
    auto next = values.erase(values.begin() + 1);
    assert(next != values.end() && *next == 30);
    assert((values == std::vector<int>{10, 30}));
    std::cout << values[0] << ' ' << values[1] << '\n';
}