#include <iostream>
using namespace std;

struct Date {
	int day;
	int month;
	int year;
};
int LeapYear(Date& a)
{
	if (a.year % 4 == 0 && a.year % 100 != 0 || a.year % 400 == 0)
	{
		return 1;
	}
	return 0;
}
int SoNgayTrongThang(Date a)
{
	switch (a.month)
	{
	case 1:
	case 3:
	case 5:
	case 7:
	case 8:
	case 10:
	case 12: return 31;
	case 4:
	case 6:
	case 9:
	case 11: return 30;
	case 2:if (LeapYear(a))
		return 29;
		  else
		return 28;
	}
}
int ValidityofDate(Date a)
{
	if (a.month > 0 && a.month < 13)
	{
		switch (a.month)
		{
		case 1:
		case 3:
		case 5:
		case 7:
		case 8:
		case 10:
		case 12: if (a.day > 0 && a.day <= 31 && a.year > 0)
			return 1;
		case 4:
		case 6:
		case 9:
		case 11: if (a.day > 0 && a.day <= 30 && a.year > 0)
			return 1;
		case 2:
			if (LeapYear(a))
			{
				if (a.day > 0 && a.day <= 29 && a.year > 0)
					return 1;
			}
			else
			{
				if (a.day > 0 && a.day <= 28 && a.year > 0)
					return 1;
			}
		}
	}
	return 0;
}
void PreviousDay(Date a)
{
	switch (a.month)
	{
		case 1:
			if (a.day == 1)
				cout << SoNgayTrongThang(a) << "/12/" << a.year-1;
			else
				cout << a.day - 1 << "/" << a.month << "/" << a.year;
			break;
		case 5:
		case 7:
		case 8:
		case 10:
		case 12:
			if (a.day == 1)
				cout << SoNgayTrongThang(a) - 1 << "/" << a.month - 1 << "/" << a.year;
			else
				cout << a.day - 1 << "/" << a.month << "/" << a.year;
			break;
		case 4:
		case 6:
		case 9:
		case 11: 
			if (a.day == 1)
				cout << SoNgayTrongThang(a) + 1 << "/" << a.month - 1 << "/" << a.year;
			else
				cout << a.day - 1 << "/" << a.month << "/" << a.year;
			break;
		case 2:
			if (a.day == 1)
				cout << "31/1/" << a.year;
			else
				cout << a.day - 1 << "/" << a.month << "/" << a.year;
			break;
		case 3:
			if (a.day == 1)
			{
				if(LeapYear(a))
					cout << "29/" << a.month - 1 << "/" << a.year;
				else
					cout << "28/" << a.month - 1 << "/" << a.year;
			}
			else
				cout << a.day - 1 << "/" << a.month << "/" << a.year;
			break;
	}
}
void NextDay(Date a)
{
	switch (a.month)
	{
		case 1:
		case 3:
		case 5:
		case 7:
		case 8:
		case 10:
			if (a.day == 31)
			cout << "1/" << a.month + 1 << "/" << a.year;
			   else
			cout << a.day + 1 << "/" << a.month << "/" << a.year;
			break;
		case 12:
			if (a.day == 31)
				cout <<  "1/1/" << a.year+1;
			else
				cout << a.day + 1 << "/" << a.month << "/" << a.year;
			break;
		case 4:
		case 6:
		case 9:
		case 11:
			if (a.day == 30)
				cout << "1/" << a.month + 1 << "/" << a.year;
			else
				cout << a.day + 1 << "/" << a.month << "/" << a.year;
			break;
		case 2:
			if (LeapYear(a))
			{
				if(a.day==29)
					cout << "1/" << a.month + 1 << "/" << a.year;
				else 
					cout << a.day + 1 << "/" << a.month << "/" << a.year;
			}
			else
			{
				if (a.day == 28)
					cout << "1/" << a.month + 1 << "/" << a.year;
				else
					cout << a.day + 1 << "/" << a.month << "/" << a.year;
			}
			break;	
	}
}
void main()
{
	Date m;
	cout << "Nhap ngay, thang, nam:";
	cin >> m.day >> m.month >> m.year;
	cout << m.day << "/" << m.month << "/" << m.year << endl;
	cout << "===============Menu==============" << endl;
	cout << " 1: Ngay hom truoc" << endl;
	cout << " 2: Ngay hom sau" << endl;
	cout << " 3: Exit " << endl;
	cout << " ================================" << endl;
	int k;
	do {
		cout << "Nhap yeu cau muon thuc hien:";
		cin >> k;
		switch (k)
		{
		case 1:
			if (ValidityofDate(m))
			{
				cout << "Ngay hom truoc:";
				PreviousDay(m);
				cout << endl;
			}
			else
				cout << "Vui long nhap lai" << endl;
			break;
		case 2:
			if (ValidityofDate(m))
			{
				cout << "Ngay hom sau:";
				NextDay(m);
				cout << endl;
			}
			else
				cout << "Vui long nhap lai" << endl;
			break;
		default: return;
		}
	} while (k > 0 && k < 2);
}