#include <bits/stdc++.h>
#define rep(begin, end) for (i=begin;i<end;i++)
#define repj(begin, end) for (j=begin;j<end;j++)
#define init(arr, end, val) for (i=0;i<end;i++) arr[i] = val;
#define printint(i0, i1) printf("%d %d\n", i0, i1)

using namespace std;
typedef long long int ll;
const int inf = 1000000000;
const int mod = 1000000007;
const int nil = -1;
int i, j, n, x, k, ans;
char c;

int main() {
    scanf(" %d %d", &n, &x);
    rep(0,n+1) {
        scanf("%c", &c);
        if (c == 'x') x = max(x-1, 0);
        else if (c == 'o') x++;
    }
    printf("%d\n", x);
}
#define _USE_MATH_DEFINES
 
#include <bits/stdc++.h>
 
using namespace std;
 
using ll = long long;
using ld = long double;
 
constexpr ll MOD = 1000000007;
 
#ifndef ONLINE_JUDGE
template <class T, class U>ostream &operator<<(ostream &o, const map<T, U>&obj) {o << "{"; for (auto &x : obj) o << " (" << x.first << " : " << x.second << ")" << ","; o << " }"; return o;}
template <class T>ostream &operator<<(ostream &o, const set<T>&obj) {o << "{"; for (auto itr = obj.begin(); itr != obj.end(); ++itr) o << (itr != obj.begin() ? ", " : "") << *itr; o << "}"; return o;}
template <class T>ostream &operator<<(ostream &o, const multiset<T>&obj) {o << "{"; for (auto itr = obj.begin(); itr != obj.end(); ++itr) o << (itr != obj.begin() ? ", " : "") << *itr; o << "}"; return o;}
template <class T>ostream &operator<<(ostream &o, const vector<T>&obj) {o << "["; for (int i = 0; i < (int)obj.size(); ++i)o << (i > 0 ? ", " : "") << obj[i]; o << "]"; return o;}
ostream &operator<<(ostream &o, const string &obj) {o << "\""; o << obj.c_str(); o << "\""; return o;}
template <class T, class U>ostream &operator<<(ostream &o, const pair<T, U>&obj) {o << "(" << obj.first << ", " << obj.second << ")"; return o;}
template <template <class tmp>  class T, class U> ostream &operator<<(ostream &o, const T<U> &obj) {o << "{"; for (auto itr = obj.begin(); itr != obj.end(); ++itr)o << (itr != obj.begin() ? ", " : "") << *itr; o << "}"; return o;}
void print_sim_py(void) {cout << endl;}
template <class Head> void print_sim_py(Head&& head) {cout << head;print_sim_py();}
template <class Head, class... Tail> void print_sim_py(Head&& head, Tail&&... tail) {cout << head << " ";print_sim_py(forward<Tail>(tail)...);}

#define print(...) print_sim_py(__VA_ARGS__);
#else
#define print(...);
#endif

template <typename... Ts>
std::istream& IN(Ts&... xs){ return (std::cin >> ... >> xs); }

#define repr(i, a, b) for (int i = a; i < b; i++)
#define rep(i, n) for (int i = 0; i < n; i++)



int main(void){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    ll n,x;
    IN(n,x);

    string s;
    IN(s);

    rep(i,n){
        switch(s[i]){
        case 'o': x++; break;
        case 'x': x=max(0ll,x-1); break;
        }
    }

    cout << x << endl;
 
    return 0;
}

