// private static string BNF = @"<expr> ::= <val> <op> <val> | <val> | 1 | 2
//
//<op> ::= + | - | *
//
//<val> ::= N_m | N_s";
public void Start(Options options)
{
CFGParser pars = new CFGParser();
var grammar = pars.readGrammarBNF(BNF);
long possibilities = CalcPossibilitiesOfDepth(grammar, 2);
System.Console.WriteLine(possibilities);
}