code: function numpf(n: number, f: string, s: string, t: string): string {
    // f - 1, 21, 31, ...
    // s - 2-4, 22-24, 32-34 ...
    // t - 5-20, 25-30, ...
    var n10 = n % 10
    if (n10 === 1 && (n === 1 || n > 20)) {
      return f
    } else if (n10 > 1 && n10 < 5 && (n > 20 || n < 10)) {
      return s
    } else {
      return t
    }
  }
docs: Belarusian