namespace std {
  class overflow_error : public runtime_error {
  public:
    explicit overflow_error(const string& what_arg);
    explicit overflow_error(const char* what_arg);
  };
}
The class overflow_error defines the type of objects thrown as exceptions to report an arithmetic overflow error.
Effects: Constructs an object of class overflow_error.
Postcondition: strcmp(what(), what_arg.c_str()) == 0.
overflow_error(const char* what_arg);
Effects: Constructs an object of class overflow_error.
Postcondition: strcmp(what(), what_arg) == 0.