По введенным с клавиатуры номеру месяца и дня определить, сколько дней осталось до Нового Года

#include <iostream>
#include <vector>
#include <algorithm>
 
using namespace std;
 
int main(void)
{
    vector<int> months = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
    int day = 0;
    int month = 0;
 
    cout << "Input day: "; cin >> day;
    cout << "Input month: "; cin >> month;
 
    if ((day < 0 || day > 31) || (month < 0 || month > 12))
    {
        cout << "-1" << endl;
        system("PAUSE");
        return EXIT_SUCCESS;
    }
 
    int sum = day;
 
    for_each(months.begin(), months.begin() + month - 1, [&sum](int x){ sum += x; });
 
    cout << "Do novogo goda stalosi " << 365 - sum << " dnei(dnea)." << endl;
 
    system("PAUSE");
    return EXIT_SUCCESS;
}

    if ((day < 0 || day > months[month - 1]) || (month < 0 || month > 12))
    {
        cout << "-1" << endl;
        system("PAUSE");
        return EXIT_SUCCESS;
    }

#include <iostream>
#include <boost/date_time/gregorian/gregorian.hpp>
 
int main()
{
    using namespace boost::gregorian;
 
    int day;
    int month;
    std::cout << "Input day: ->"; std::cin >> day;
    std::cout << "Input month: ->"; std::cin >> month;
 
    partial_date pd(day, month);
    date today = day_clock::local_day();
    date d = pd.get_date(today.year());
 
    partial_date new_years_day(1, Jan);
    days days_until_year_start = new_years_day.get_date(today.year()+1) - d;
    std::cout << "Days until next Jan 1: " << days_until_year_start.days()
              << std::endl;
 
    return 0;
}