function getSlavicForm(c) {
    if (Math.floor(c) !== c) {
      return 2;
    }
    if (
      (c % 100 >= 5 && c % 100 <= 20) ||
      (c % 10 >= 5 && c % 10 <= 9) ||
      c % 10 === 0
    ) {
      return 0;
    }
    if (c % 10 === 1) {
      return 1;
    }
    if (c > 1) {
      return 2;
    }
    return 0;
  }
@internal
@param {Piece} piece
@param {Language} language
@param {Pick<Required<Options>, "decimal" | "spacer" | "maxDecimalPoints" | "digitReplacements">} options