Untitled

#include <iostream>
using namespace std;
int difference, day, month, year, leapyear;

int main()

{
    cout << "\n Enter the difference in days and press Enter : ";
    cin >> difference;

    cout << "\n Enter a date in the form of DD MM YYYY and press enter: ";
    cin >> day >> month >> year;

    if ((year % 4 == 0 && year % 100 != 0) || (year % 400 == 0))
    {
        leapyear = 1;
    }
    else
    {
        leapyear = 0;
    }
    day = day + difference;
    if ((month == 4) || (month == 6) || (month == 9) || (month == 11))
    {
        if (day > 30)
        {
            //
            day -= 30;
            month++;
        }
        else if (day < 1)
        {
            month--;
            day = day + 31;
        }
    }
    if ((month == 1) || (month == 3) || (month == 5) || (month == 7) || (month == 8) || (month == 10) || (month == 12))
    {
        if (day > 31)
        {
            day = day - 31;
            month++;
            if (month == 13)
                month = 1;
            year++;
        }
    }

    if (day < 1)
    {
        month--;
        if (month == 0)
        {
            day = day + 31;
            month = 12;
            year--;
        }
        else if (month == 2)
        {
            if (leapyear == 1)
            {
                if (day > 29)
                {
                    day = day - 29;
                    month;
                }

                else
                {
                    if (day > 28)
                    {
                        day = day - 28;
                        month++;
                    }
                    else
                    {
                        day = day + 31;
                    }
                }
            }
        }
    }
    cout << "\n The final date is: " << day << "/" << month << "/" << year << endl;