private static void CalculateSalary(Employee employee)
        {
            if (visitedEmplyees.Contains(employee.Id))
            {
                return;
            }

            if (employee.Subordinates.Count == 0)
            {
                employee.Salary = 1;
                return;
            }

            visitedEmplyees.Add(employee.Id);

            foreach (var subordinate in employee.Subordinates)
            {
                CalculateSalary(subordinate);
                employee.Salary += subordinate.Salary;
            }
        }
 public void AddSubordinate(Employee employee)
 {
     this.Subordinates.Add(employee);
 }