package main

import (
	"fmt"
	"strings"
)

func main() {
	var n, m int
	fmt.Scan(&n, &m)
	var s string
	cnt := 0
	for i := 0; i < n; i++ {
		fmt.Scan(&s)
		cnt += strings.Count(s, "R")
	}
	fmt.Println(n*m - cnt)
}