Class Air

12.23-constexprStaticInitFiasco0/main.cpp:6–16

#include <cstdio>

struct Air {
  Air(int amount)
  : _amount{amount}
  {}

  void Consume(int v) { _amount -= v; }
  int  Available() const { return _amount; }

private:
  int _amount;
};

struct Human {
  Human(int breath);