using System; class Program { static void Main() { Console.Write("Enter a number: "); int n = int.Parse(Console.ReadLine()); bool isPrime = n > 1; for(int i = 2; i <= Math.Sqrt(n); i++) { if(n % i == 0) { isPrime = false; break; } } Console.WriteLine(isPrime ? "Prime" : "Not prime"); } }