import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner in = new Scanner(System.in);
        int N = in.nextInt();
        int M = in.nextInt();
        final int total = N * M;
        int count = 0;

        for(int i=0; i<=N; i++){
            String L = in.nextLine();
            String[] arr = L.split("");
            for(int j=0; j<arr.length; j++){
                if(arr[j].equals("R")){
                    count++;                    
                }
            }
        }
        System.out.println(total - count);

    }
}