```go
package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

func main() {
	scanner := bufio.NewScanner(os.Stdin)
	scanner.Split(bufio.ScanWords)

	writer := bufio.NewWriter(os.Stdout)
	defer writer.Flush()

	// Read number of queries
	if !scanner.Scan() {
		return
	}
	q, _ := strconv.Atoi(scanner.Text())

	// Array to store position of each book ID.
	// Max ID is 2*10^5.
	pos := make([]int, 200005)

	// Initialize pointers for the left and right ends of the shelf.
	// Using l=1, r=0 ensures that the first insertion (whether L or R)
	// sets the range to size 1 correctly.
	// If L: l becomes 0. Range [0, 0].
	// If R: r becomes 1. Range [1, 1].
	l := 1
	r := 0

	for i := 0; i < q; i++ {
		scanner.Scan()
		op := scanner.Text()[0] // 'L', 'R', or '?'
		scanner.Scan()
		id, _ := strconv.Atoi(scanner.Text())

		if op == 'L' {
			l--
			pos[id] = l
		} else if op == 'R' {
			r++
			pos[id] = r
		} else {
			// Query '?'
			// Calculate books to remove from left vs right
			fromLeft := pos[id] - l
			fromRight := r - pos[id]

			if fromLeft < fromRight {
				fmt.Fprintln(writer, fromLeft)
			} else {
				fmt.Fprintln(writer, fromRight)
			}
		}
	}
}
```