import java.io.*;
import java.util.*;
//ECOO - question 1, 2018
//scores perfectly
public class question1 {
	public static void main(String args[]) {

		try {
			Scanner in=new Scanner(new FileReader("DATA12.txt"));
			for(int m=0; m<10; m++) {
				int Bcount=0;
				int daysPlays = in.nextInt();
				int daysCollect = in.nextInt();
				int numberLeft=0;

				for(int i=0; i<daysCollect; i++) {
					String boxOrNot=in.next();
					if(Bcount!=0 && boxOrNot.equals("E")&&numberLeft>0)
						numberLeft--;
					else if(boxOrNot.equals("B")) {
						numberLeft+=daysPlays-1;
						Bcount++;
					}
				}

				if(numberLeft<=0)
					System.out.println("0");
				else
					System.out.println(numberLeft);
			}
		} catch (IOException e) {
			System.out.println("error");
		}
	}
}