STDIN

1. Rust - read input from STDIN
2. Rust - read STDIN - remove trailing newline (trim, chomp)
3. Rust - flush STDOUT - read STDIN
4. Get number from STDIN
5. Get number from STDIN - same variable
6. Get number (i32) in using a function
7. Exercise: STDIN rectangle
8. Exercise: STDIN circle
9. Exercise: STDIN calculator
10. Solution STDIN rectangle
11. Solution: STDIN calculator