public static void Main()
Console.WriteLine("กรุณากรอกคะแนน");
scoreTextbox = Convert.ToInt32(Console.ReadLine());
if(scoreTextbox >=80 && scoreTextbox <=100){
else if(scoreTextbox >=70 && scoreTextbox <=79){
else if(scoreTextbox >=60 && scoreTextbox <=69){
else if(scoreTextbox >=50 && scoreTextbox <=59){