#include<bits/stdc++.h>
using namespace std;
#define IOS ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define endl "\n"
#define frfr  freopen("input.text","r",stdin); //freopen("output.text","w",stdout)
#define ll long long int
#define wh int T;cin >> T;while(T--)
#define foro(i,n) for(int i=0;i<n;i++)

void solve(){
	int n,x;
	cin >> n >> x;
	string s;
	cin >> s;
	for(int i : s){
		if(i == 'o'){
			x++;
		}else{
		   if(x != 0) x--;	
		}
	}
	cout << x << endl;
}
int main()
{
    
	   solve();
	
 return 0;	
}



#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define all(v) v.begin(), v.end()
#define rep(i, n) for (ll i = 0; i < (ll)(n); i++)
#define repr(i, n) for (ll i = (n-1); i >= 0; i--)
#define Rep(n) for (ll _ = 0; _ < (ll)(n); _++)

template <class S>S sum(vector<S>& a) {return accumulate(all(a), S());}
template <class S>S max(vector<S>& a) {return *max_element(all(a));}
template <class S>S min(vector<S>& a) {return *min_element(all(a));}
ll max(int a, ll b) { return max((ll)a, b); } ll max(ll a, int b) { return max(a, (ll)b); }
ll min(int a, ll b) { return min((ll)a, b); } ll min(ll a, int b) { return min(a, (ll)b); }

void Main();
int main() {
  cin.tie(nullptr);
  ios_base::sync_with_stdio(false);
  cout << fixed << setprecision(20);
  Main();
  return 0;
}

void Main(){
  int n,x; cin >> n >> x;
  string s; cin >> s;
  for(char a: s){
    if(a == 'o'){
      x++;
    }else{
      x = max(0, x-1);
    }
  }
  cout << x << endl;
}
