#include<bits/stdc++.h>
using namespace std;
typedef long long ll; typedef double db;
typedef pair<int, int> pii; typedef pair<ll, ll> pll;
typedef vector<int> vi; typedef vector<ll> vl;
typedef vector<pii> vpii; typedef vector<pll> vpll;
#define FOR(n) for(int i=0;i<n;++i)
#define IOS ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
ll gcd(ll a, ll b) { return a % b ? gcd(b, a % b) : b; }
const ll mod = 1e9 + 7; const ll inf = 0x3f3f3f3f;
ll qpow(ll a, ll b) { ll t = 1; while (b != 0) { if (b & 1)t = (t * a) % mod; a = (a * a) % mod; b >>= 1; }return t; }
int n, x;
string s;
signed main() {
	cin >> n >> x;
	cin >> s;
	for (auto& ch : s) {
		if (ch == 'o')++x;
		else {
			if (x)--x;
		}
	}
	cout << x << endl;
	return 0;
}
//Bismillahirrahmanirrahim

#pragma GCC optimize ("O3")
#pragma GCC target ("sse4")
#include <bits/stdc++.h>

using namespace std;

typedef long long lo; 
typedef pair< lo,lo > PII;

#define fi first
#define se second
#define mp make_pair
#define endl "\n"
#define pb push_back
#define fio() ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL)
#define FOR for(int i=1;i<=n;i++)
#define mid ((start+end)/2)
#define ort ((bas+son)/2)

const lo inf = 1000000000000000000;
const lo KOK = 100000;
const lo LOG = 30;
const lo li = 500005;
const lo mod = 1000000007;

int n,m,b[li],a[li],k,flag,t;
int cev;
string s;
vector<int> v;

int main(void){
	fio();
	cin>>n>>k>>s;
	for(auto go:s){
		//~ cout<<go<<endl;
		if(go=='o')k++;
		if(go=='x' && k!=0)k--;
	}
	cout<<k<<endl;
	return 0;
}


