Polina Favorskaya (Russian: Polina Favorskaia, born 21 November 1991 in Volgograd, Russia) was the replacement of Elena Temnikova, who was introduced 5 June 2014. Favorskaya announced she was leaving the group in August 2017, but continued performing with them until the end of 2017.  Anastasia Karpova (Russian: Anastasiia Karpova, born 2 November 1984 in Balakovo, Russia) was very interested in music since her early age, but dedicated herself to ballet. She was also attending singing classes and decided to pursue her singing career. Anastasia had replaced Lizorkina, after the latter announced her departure. She first had her debut with the group on their single "Like Mary Warner". Anastasia, along with Elena and Olga had recorded their second studio album Mama Lover, making it Karpova's first full-length studio album. Karpova decided to leave the group to pursue a solo career. The song "UGAR" was her last song with the group.  Marina Lizorkina (Russian: Marina Lizorkina, born 9 June 1983 in Moscow, Russia) entered the Contemporary Art University in Moscow at the age of sixteen. She used to sing in a choir, before she became the lead singer of the group "Formula". In 2004, they released a few singles for the series Obrechennaya Stat Zvezdoy. Lizorkina was the last to join Serebro, after she saw an Internet announcement.  Dasha Shashina (Russian: Dasha Shashina, born 1 September 1990 in Nizhny Novgorod, Russia) is the replacement of Anastasia Karpova, who began performing with the group in October 2013. Shashina left the group in March 2016 due to serious health issues and having to undergo two surgeries.  Elena Temnikova (Russian: Elena Temnikova, born 18 April 1985 in Kurgan, Russia) came to media prominence as a contestant on the Channel One talent show Star Factory in 2003. She was spotted by Maxim Fadeev, the main producer of Star Factory, and signed to his recording company Monolit Records. Although Temnikova released two disco singles, "Begi" and "Taina", she did not continue her solo career and joined Serebro instead. She married co-member of Star Factory Alexey Semenov; the two separated in 2007, before a settlement for divorce. She then had a brief conflict with Fedeev, after dating and subsequently leaving his brother. She currently resides in Moscow, Russia. On 15 May 2014 the official Serebro website reported that Elena had left the group due to ill health. She was replaced with Karpova who had left the band earlier the previous year until they find a replacement.

Answer this question "How many former members were there in the band??" by extracting the answer from the text above.
Shashina left the group in March 2016 due to serious health issues and having to undergo two surgeries.