Write a program to swap two numbers without using third number

Code:

using System;

namespace ProgrammingQuestion
{
 class Program
 {
   static void Main(string[] args)
   {
     //Variable Declaration
     string firstVal, secondVal;
     int firstNum, secondNum;
     
     //User Input
     Console.Write("Enter First Number:");
     firstVal = Console.ReadLine();
     firstNum = Convert.ToInt32(firstVal);
     Console.Write("Enter Second Number:");
     secondVal = Console.ReadLine();
     secondNum = Convert.ToInt32(secondVal);
     
     //Swapping Logic
     secondNum = firstNum + secondNum;
     firstNum = secondNum - firstNum;
     secondNum = secondNum - firstNum;
     
     //Print Result
     Console.WriteLine("Numbers After Swapping:");
     Console.WriteLine($"First Number:{firstNum}, Second Number:{secondNum}");
     Console.Read();
   }
 }
}

Output:

Enter First Number:5
Enter Second Number:7
Numbers After Swapping:
First Number:7, Second Number:5