how many prime numbers are there total? in csharp

main.cs
using System;

class Program {
    static bool IsPrime(int n) {
        if (n < 2) {
            return false;
        }
        for (int i = 2; i <= Math.Sqrt(n); i++) {
            if (n % i == 0) {
                return false;
            }
        }
        return true;
    }
    
    static void Main(string[] args) {
        Console.WriteLine("Enter a number:");
        int n = int.Parse(Console.ReadLine());
        int count = 0;
        for (int i = 2; i <= n; i++) {
            if (IsPrime(i)) {
                count++;
            }
        }
        Console.WriteLine("There are " + count + " prime numbers between 2 and " + n);
    }
}
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