import java.util.Scanner;

public class Main {
	public static void main(String[]args) {
		Scanner scan=new Scanner(System.in);
		int h=scan.nextInt();//在湖底时到水面的距离
		int s=scan.nextInt();//最初水下深度
		String str=scan.next();//指令
		scan.close();
		
		for(int i=0;i<str.length();i++) {
			char ch=str.charAt(i);
			if(ch=='u') {//上浮
				if(s>0)
					s-=1;
			}
			else if(ch=='d') {//下沉
				if(s<h)
				    s+=1;
			}
		}
		
		System.out.println(s);
	}

}
/**************************************************************
	Problem: 1826
	User: admin
	Language: Java
	Result: Accepted
	Time:4098 ms
	Memory:40352 kb
****************************************************************/