datePlusPlusFragment

#include <iostream>

int main()
{

    int day{};
    int month{};
    int year{};

    std::cout << "Enter day: "; std::cin >> day;
    std::cout << "Enter month: "; std::cin >> month;
    std::cout << "Enter year: "; std::cin >> year;

    const int monthInYear = 12;
    const int daysInMonth{30 + ((month < 8 and month % 2 != 0) or (month >= 8 and month % 2 == 0)) + (month == 2)*(-2 + ((((year % 400 == 0) or (year % 4 == 0)) and (year % 100 != 0))))};

    std::cout << daysInMonth << '\n';

/// ? ? ? :) :) :)
}