vv

using System;
using System.Text;
using System.Text.RegularExpressions;

class MainClass
{
   public static void Main (string[] args)
  {
    string chislo = @"([1-9]\d*|[0])";
    string znach = @"[a-z0-9]";

    string correct_var = $@"(([a-z]{znach}*)|{chislo})";
    string arifmetic_in_mas = $@"(\s*{correct_var}\s*[-+/*])";
    string long_pattern_in_mas = $@"(({arifmetic_in_mas}*)\s*{correct_var}\s*)";

    //string massiv = $@"[a-z]{znach}*(\[({correct_var}|{long_pattern_in_mas})\])?";
    string fun = $@"[a-z]{znach}*(\(({correct_var}|{long_pattern_in_mas})\))";

    //string arifmetic = $"({correct_var}|{massiv}|{fun})";
    //string pattern_arifmetic = $@"(\s*{arifmetic}\s*[-+*/])";
    //string long_pattern_arifmetic = $@"(({pattern_arifmetic}*)\s*{arifmetic})";

    //string pattern = $@"[a-z]{znach}*\s*=\s*({long_pattern_arifmetic}|{massiv}|{fun}|{chislo})\s*;";
    string str;

    while((str = Console.ReadLine())!= null)
      foreach (Match match in Regex.Matches(str, correct_var))
         Console.WriteLine(match.Value);
  }
}