/* 1
Console.Write("Введите год: ");
int year21 = int.Parse(Console.ReadLine());
for (int year = 1900; year <= 1999; year++)
{
    for (int month = 1; month <= 12; month++)
    {
        
        for (int day = 1; day < DateTime.DaysInMonth(year,month); day++)
        {
            bool a = dob(year21, year, month, day);
            if (a == true)
            {
                Console.WriteLine( new DateTime(year,month,day).ToShortDateString());
            }
        }
    }
}

static bool dob(int year21, int year, int moth, int day)
{
    int sq = 0;
    foreach (var numb in year.ToString())
    {
        sq += Convert.ToInt32(numb.ToString()) * Convert.ToInt32(numb.ToString());
    }

    if (sq - day * day == year21 - year)
    {
        return true;
    }
    else
    {
        return false;
    }
}
*/

/* 2
Console.Write("string: ");
string str = Console.ReadLine();
string newstr = "";
int count = 1;
for (int i = 0; i < str.Length; i++)
{
    if (i == str.Length - 1 || str[i] != str[i + 1])
    {
        if (count == 1)
        {
            newstr += str[i];
            count = 1;
        }
        else
        {
            newstr += count.ToString() + str[i];
            count = 1;
        }
    }
    else
    {
        count++;
    }
}
Console.WriteLine(newstr);
*/

/* 3
Console.Write("Загадайте число: ");
string numbertrue = Console.ReadLine();
Console.Write("Предположите число: ");
string numbertry = Console.ReadLine();
Console.WriteLine($"Быков: {bulls(numbertrue,numbertry)}, коров: {cows(numbertrue,numbertry)}");

static int bulls(string str1, string str2)
{
    int bulls = 0;
    for (int i = 0; i < str1.Length; i++)
    {
        if (str1[i] == str2[i])
        {
            bulls++;
        }
    }

    return bulls;
}

static int cows(string str1, string str2)
{
    int cows = 0;
    for (int i = 0; i < str1.Length; i++)
    {
        for (int j = 0; j < str2.Length; j++)
        {
            if (str1 [i] == str2[j])
            {
                if (i != j)
                {
                    cows++;
                }
            }
        }
    }

    return cows;
}
*/