#include <iostream>
#include <iomanip>
#include <fstream>
#include <string>
#include <windows.h>
#include <conio.h>
#include <stdio.h>
#include <cwchar>
#include <winuser.h>
#include <tchar.h>
using namespace std;

// ==========ПЕРЕМЕЩЕНИЕ КУРСОРА НА ВЫБРАННУЮ ПОЗИЦИЮ==========
void gotoxy(int xpos, int ypos)
{
    COORD scrn;
    HANDLE hOuput = GetStdHandle(STD_OUTPUT_HANDLE);
    scrn.X = xpos; scrn.Y = ypos;
    SetConsoleCursorPosition(hOuput, scrn);
}

bool valid_date(int _Year, int _Month, int _DayNo)
{
    int days_in_month[] = { 0,31,28,31,30,31,30,31,31,30,31,30,31 };

    if (_Year % 4 == 0)
        days_in_month[2] = 29;

    if ((_Month < 1) || (_Month > 12))
        return false;

    if ((_DayNo < 1) ||  (_DayNo > days_in_month[_Month]))
        return false;

    return true;
}

int main()
{

    int length = 0;
    int pospos = 0;
    int posarrays[8] = { 0, 1, 3, 4, 6, 7, 8, 9 };
    int pos = posarrays[pospos];
    string mask1 = "__.__.____";
    cout << mask1;
    while (length != 8) {
        int ch = _getch();
        if (ch == 8 && length != 0) {
            length--;
            mask1[pos - ((length == 3 || length == 1) ? 2 : 1)] = '_'; // пропускаем точки
            gotoxy(0, 0);
            pospos--;
            pos = posarrays[pospos];
            cout << mask1;
        } else if (ch >= '0' && ch <= '9') {
            length++;
            mask1[pos] = ch;
            gotoxy(0, 0);
            pospos++;
            pos = posarrays[pospos];
            cout << mask1;
        }
    }

    string d = mask1.substr(0, 2);
    string m = mask1.substr(3, 2);
    string y = mask1.substr(6, 4);

    if (valid_date(stoi(y), stoi(m), stoi(d))) {
        cout << "ok";
    }
    else cout << "error";


    return 0;
}