#include <iostream>
#include <memory>
#include <vector>

class Estimate {
public:
    virtual int minutes() const = 0;
    virtual ~Estimate() = default;
};
class Walking final : public Estimate {
public: int minutes() const override { return 40; }
};
class Cycling final : public Estimate {
public: int minutes() const override { return 18; }
};

int main() {
    std::vector<std::unique_ptr<Estimate>> policies;
    policies.push_back(std::make_unique<Walking>());
    policies.push_back(std::make_unique<Cycling>());
    for (const auto& policy : policies) { std::cout << policy->minutes() << " minutes\n"; }
}