How many million inhabitants did Czechoslovakia have before the split in 1993?

Explanation

Czechoslovakia was a republic formed on 28 October 1918 after the end of World War I. The country was a sovereign state until it became occupied by Germany in 1938. Later, it came under the influence of the USSR. Mikhail Gorbachev's perestroika policy did open the country to democracy, however, and the author Václav Havel (1936-2011) was elected president. On 1 January 1993, the country peacefully split into two states: the Czech Republic and Slovakia. Havel thus also became the last president of Czechoslovakia.