C# code: using System; using System.Collections.Generic; using System.IO;

class Solution { static void Main(String[] args) { int i = 4; double d = 4.0; string s = "HackerRank ";

    // Declare second integer, double, and String variables.
    int userInt;
    double userDouble;
    string userString;

    // Read input for the declared variables.
    userInt = Convert.ToInt32(Console.ReadLine());       // Read an integer
    userDouble = Convert.ToDouble(Console.ReadLine());   // Read a double
    userString = Console.ReadLine();                     // Read a string

    // Perform the operations and print the results
    // Print the sum of integer variables
    Console.WriteLine(i + userInt);

    // Print the sum of double variables to one decimal place
    Console.WriteLine($"{d + userDouble:F1}");

    // Concatenate and print the strings
    Console.WriteLine(s + userString);