To solve your problem, you could use a lookup table:
Dictionary<string,> dictionary = new Dictionary<string,>();
dictionary.Add("C", 10);
dictionary.Add("D", 12);
dictionary.Add("L", 14);
dictionary.Add("K", 15);
dictionary.Add("B", 13);
And then in a loop to change all letters to numbers
if (dictionary.ContainsKey("С"))
{
int value = dictionary["С"];
}
Good luck!