3d.cc

#include <iostream>

int main() {
    int month;
    int year;
    std::cin >> month >> year;

    switch (month)
    {
    case 1:
    case 3:
    case 5:
    case 7:
    case 8:
    case 10:
    case 12:
        std::cout << 31 << std::endl;
        break;
    case 2:
        if (year % 400 == 0)
        {
            std::cout << 29 << std::endl;
        }
        else if (year % 100 == 0)
        {
            std::cout << 28 << std::endl;
        }
        else if (year % 4 == 0)
        {
            std::cout << 29 << std::endl;
        }
        else
        {
            std::cout << 28 << std::endl;
        }
        break;
    case 4:
    case 6:
    case 9:
    case 11:
        std::cout << 30 << std::endl;
        break;
    }
}