class Company {
  constructor() {
    this.departments = {};
  }

  addEmployee(name, salary, position, department) {
    if (!(name && salary && position && department) || salary < 0) {
      throw new Error('Invalid input!');
    }

    if (!this.departments.hasOwnProperty(department)) {
      this.departments[department] = [];
    }

    this.departments[department].push({ name, salary, position });
    return `New employee is hired. Name: ${name}. Position: ${position}`;
  }

  bestDepartment() {
    let bestDepartment = '';
    let avgSalary = 0;

    for (let [department, employees] of Object.entries(this.departments)) {
      let depAvgSalary = employees.reduce((acc, e) => acc + Number(e.salary), 0);
      depAvgSalary /= employees.length;

      if (depAvgSalary > avgSalary) {
        bestDepartment = department;
        avgSalary = depAvgSalary;
      }
    }

    const sortedBySalaries = this.departments[bestDepartment]
      .sort((a, b) => b.salary - a.salary || a.name.localeCompare(b.name))
      .map((x) => `${x.name} ${x.salary} ${x.position}`)
      .join('\n')

    return `Best Department is: ${bestDepartment}\nAverage salary: ${avgSalary.toFixed(2)}\n${sortedBySalaries}`;
  }