Performers take part in the 13th Polish Fire Festival in Ostroda, Poland, on Aug. 24, 2018. The 13th Polish Fire Festival is held here from Aug. 21 to Aug. 26. (Xinhua/Chen Xu)

Performers take part in the 13th Polish Fire Festival in Ostroda, Poland, on Aug. 24, 2018. The 13th Polish Fire Festival is held here from Aug. 21 to Aug. 26. (Xinhua/Chen Xu)

Performers take part in the 13th Polish Fire Festival in Ostroda, Poland, on Aug. 24, 2018. The 13th Polish Fire Festival is held here from Aug. 21 to Aug. 26. (Xinhua/Chen Xu)

Performers take part in the 13th Polish Fire Festival in Ostroda, Poland, on Aug. 24, 2018. The 13th Polish Fire Festival is held here from Aug. 21 to Aug. 26. (Xinhua/Chen Xu)

Performers take part in the 13th Polish Fire Festival in Ostroda, Poland, on Aug. 24, 2018. The 13th Polish Fire Festival is held here from Aug. 21 to Aug. 26. (Xinhua/Chen Xu)

Performers take part in the 13th Polish Fire Festival in Ostroda, Poland, on Aug. 24, 2018. The 13th Polish Fire Festival is held here from Aug. 21 to Aug. 26. (Xinhua/Chen Xu)

Performers take part in the 13th Polish Fire Festival in Ostroda, Poland, on Aug. 24, 2018. The 13th Polish Fire Festival is held here from Aug. 21 to Aug. 26. (Xinhua/Chen Xu)