`A` `=` `(` `1` `-` `2/2.3` `)` `.` `(` `1` `-` `2/3.4` `)` `.` `(` `1` `-` `2/4.5` `)` `...` `(` `1` `-` `2/2020 . 2021` `)`
`A` `=` `(` `6/2.3` `-` `2/2.3` `)` `.` `(` `12/3.4` `-` `2/3.4` `)` `.` `(` `20/4.5` `-` `2/4.5` `)` `....` `(` `4082420/2020.2021` `-` `2/2020.2021` `)`
`A` `=` `4/2.3` `.` `10/3.4` `.` `18/4.5` `...` $\frac{4082418}{2020.2021}$
`A` `=` `1.4/2.3` `.` `2.5/3.4` `.` `3.6/4.5` `...` `2019.2022/2020.2021`
`A` `=` `(1.2.3...2019)/(2.3...2020)` `.` `(4.5.6...2022)/(3.4...2021)`
`A` `=` `1/2020` `.` `2022/3`
`A` `=` `2022/6060`
`A` = `337/1010`
