package main

import (
	"fmt"
)

func main() {
	var n int
	var s string
	fmt.Scan(&n, &s)

	ans := 0
	lastChar := '.'
	lastPos := -1

	for i, c := range s {
		if c == 'L' {
			if lastChar == 'R' {
				if (i-lastPos-1)%2 == 1 {
					ans++
				}
			}
			lastChar = 'L'
			lastPos = i
		} else if c == 'R' {
			if lastChar == '.' {
				ans += i
			} else if lastChar == 'L' {
				ans += i - lastPos - 1
			}
			lastChar = 'R'
			lastPos = i
		}
	}

	if lastChar == '.' {
		ans = n
	} else if lastChar == 'L' {
		ans += n - 1 - lastPos
	}

	fmt.Println(ans)
}