Console.WriteLine("cual es las nota")
If n=19 or n=20 then console.WriteLine("A")
If n=16 or n=18 or n=17 then console.WriteLine("B")
If n=15 or n=13 or n=14 then console.WriteLine("C")
If n=12 or n=11 or n=9 then console.WriteLine("D")
If n>9 then console.WriteLine("E")