#include <vector>
#include <iostream>

int main() {
    std::vector<int> v { 1, 2, 3, 4 };
    v.reserve(5);
    std::cout << "capacity: " << v.capacity() << std::endl;
    v.reserve(10);
    std::cout << "capacity: " << v.capacity() << std::endl;
    v.reserve(5);
    std::cout << "capacity: " << v.capacity() << std::endl;
    v.shrink_to_fit();
    std::cout << "capacity: " << v.capacity() << std::endl;
}