using System;

​

    // Prompt the user to enter the day and month.

    Console.Write("Enter today's day of the month: ");

    int day = int.Parse(Console.ReadLine());

​

    Console.Write("Enter today's month (number): ");

    int month = int.Parse(Console.ReadLine());

​

    // Determine today's date.

    DateTime today = new DateTime(DateTime.Now.Year, month, day);

​

    // Determine the year of the summer solstice.

    int year = today.Month >= 12 && today.Day >= 21 ? today.Year + 1 : today.Year;

​

    // Determine the date of the summer solstice.

    DateTime summerSolstice = new DateTime(year, 12, 21);

​

    // Determine the number of days until summer starts.

    int daysUntilSummer = (int)(summerSolstice - today).TotalDays;

​

    if (daysUntilSummer < 0) {

      // Summer has already started this year, so calculate the number of days until next summer.

      summerSolstice = new DateTime(year + 1, 12, 21);

      daysUntilSummer = (int)(summerSolstice - today).TotalDays;

    }

​

    Console.WriteLine($"Days until summer starts: {daysUntilSummer}");