loop.cs

using System;
using System.Text;

namespace C_sharp
{
    class Program
    {
        static void Main(string[] args)
        {
            int N = int.Parse(Console.ReadLine());

            StringBuilder sb = new StringBuilder();

            for (int i = 0; i < N; i++)
            {
                for (int j = 0; j < N; j++)
                {
                    if (i > j)
                    {
                        sb.Append(" ");
                    }
                    else
                    {
                        sb.Append("*");
                    }
                }
                sb.Append("\n");
            }

            Console.WriteLine(sb);
        }
    }
}