#include <iostream>
using namespace std;
int main(){
	int h,s;
	cin>>h>>s; 
	string a;
	cin>>a;
	for(int i=0;i<a.size();i++){
		if(a[i]=='u'&&s!=0){
			s--;
		}
		if(a[i]=='d'&&s<h){
			s++;
		}
	} 
	cout<<s; 
    return 0;
}
/**************************************************************
	Problem: 1826
	User: panyuchen
	Language: C++
	Result: Accepted
	Time:41 ms
	Memory:2076 kb
****************************************************************/