#include <iostream>
#include <string>
#include <array>

struct Date
{
  int year;
  int month;
  int day;
};

bool is_leap_year(int year)
{
  if ( year % 400 == 0 )
    return true;
  if ( year % 100 == 0 )
    return false;
  return year % 4 == 0;
}

int days_in_month(int year, int month)
{
  static constexpr const std::array<int, 13> days
  {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
  
  if (month < 1 || month > 12)
    return 0;
  
  if ( month == 2 && is_leap_year( year ) )
    return 29;
    
  return days.at(month);
}

Date create_date(int year, int month, int day)
{
  if ( month < 1 || month > 12 )
  {
    throw std::domain_error{"Month " + std::to_string(month) + " doesn't exist!"};
  }
  
  if (  day < 1 || day > days_in_month( year, month ) )
  {
    throw std::domain_error{"Day " + std::to_string(day) + " invalid"};
  }
  
  return {year, month, day};
}

void print(std::ostream& os, struct Date const& d)
{
  os << d.year << "-"
     << d.month << "-"
     << d.day;
}