C# assignment which i failed today. Convert.ToInt issue?

Hi everyone. Today i had my first exam going over the basics and i stumbled on this small project.
The idea is you input up to 5 number (0-9), if less are given we add 0’s in the front.
Then we add them up individually, so for example 12345 becomes 1+2+3+4+5 and the total is 15.
Its supposed to be very simple but i have no clue what is going wrong here.
Any help is explaining is much appreciated.

using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; namespace TussentijdseEvaluatie1 { public class Permanente { public static void SomVanCijfers() { Console.WriteLine("Gelieve een getal in te voeren dat bestaat uit exact 5 decimale cijfers."); string getalInput = Console.ReadLine(); while (getalInput.Length < 5) { getalInput = $"0{getalInput}"; } // check variable getalInput after the loop (value and type) Console.WriteLine(getalInput); Console.WriteLine(getalInput.GetType()); // converting to ints (after it kept failing) i guess it starts failing here but i'm not sure why? int getalInput1 = Convert.ToInt16(getalInput[0]); int getalInput2 = Convert.ToInt16(getalInput[1]); int getalInput3 = Convert.ToInt16(getalInput[2]); int getalInput4 = Convert.ToInt16(getalInput[3]); int getalInput5 = Convert.ToInt16(getalInput[4]); // Just making sure its converted Console.WriteLine(getalInput1.GetType()); Console.WriteLine(getalInput2.GetType()); Console.WriteLine(getalInput3.GetType()); Console.WriteLine(getalInput4.GetType()); Console.WriteLine(getalInput5.GetType()); // checking if the numbers are correct (They are) Console.WriteLine(getalInput1); Console.WriteLine(getalInput2); Console.WriteLine(getalInput3); Console.WriteLine(getalInput4); Console.WriteLine(getalInput5); // this was so i could see what exactly i was adding up. Console.WriteLine($"De som is: {getalInput1} + {getalInput2} + {getalInput3} + {getalInput4} + {getalInput5}"); Console.WriteLine($"De som is: {Convert.ToInt16(getalInput[0]) + Convert.ToInt16(getalInput[1]) + Convert.ToInt16(getalInput[2]) + Convert.ToInt16(getalInput[3]) + Convert.ToInt16(getalInput[4])}"); } } }