#include <bits/stdc++.h>

using namespace std;
#define  ll long long
#define ld long double
#define f first
#define s second


int main()
{
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

    ll n,x;
    string s;

    cin >> n >> x >> s;
    for(int i=0; i<n; i++)
    {
        if (s[i]=='x')
        {
            if (x) x--;
        }
        else
            x++;
    }

    cout << x << '\n';

    return 0;
}

#include<bits/stdc++.h>
#include<iostream>
#include<algorithm>
#include<unordered_map>
#include<vector>
#include<unordered_set>
#include<set>
#include<map>
#include<queue>
#include<stack>
#include<string>
//Required Headers
using namespace std;

#define PI 3.1415926535897932384626
#define sp(x,y)                     fixed<<setprecision(y)<<x
#define mk(arr,n,type)              type *arr=new type[n]; // dynamic allocation of memory
#define del(arr)                    delete []arr;           // deletion of allocated memory
const int mod = 1'000'000'007;
const int inf = 1e9 + 5;

//for loops

#define fo(i, n) for(i=0; i<n; i++) 
#define Fo(i,k,n) for(i=k;k<n?i<n:i>n;k<n?i+=1:i-=1)
#define fo2(i, n,t) for(i=0; i<n; i+=t) 

//essentials

#define tc(t)               ll t;ll i; cin>>t; fo(i,t)
#define ll long long

//STL

#define pb push_back
#define mp make_pair
#define F first
#define S second
#define vbe(x) x.begin(), x.end()
#define sortvbe(x) sort(vbe(x))
#define setit(it, a) for(auto it = a.begin(); it != a.end(); it++)
typedef map<int,int>    mii;
typedef map<ll,ll>      mll;
typedef pair<int, int>  pii;
typedef pair<ll, ll>  pl;
typedef vector<int>   vi;
typedef vector<ll>    vl;
typedef vector<pii>   vpii;
typedef vector<pl>    vpl;
typedef vector<vi>    vvi;
typedef vector<vl>    vvl;
typedef set<int>        si;
typedef set<ll>         sl;


//inputs

#define ci(x)     cin>>x;
#define ci2(x,y)    cin>>x>>y;

//template<typename... T>
//void read(T&... args) {
//  ((cin >> args), ...);
//}

//outputs

#define pi(x)     cout<<x;
#define pinl(x)     cout<<x<<endl;

//template<typename... T>
//void write(T&&... args) { //rvalue reference is new to C++ 
//  ((cout << args << " "), ...);
//}
ll m=1000000007;
//some imp func

inline int gcd(int a,int b) {if (a==0) return b; else return gcd(b%a,a);}
inline void take_input(int A[],int n){for(int i=0;i<n;i++){ cin>>A[i];}}
inline void show(int *A,int n){for(int i=0;i<n;i++){cout<<A[i]<<" ";}cout<<endl;}
inline bool sortbysec(const pair<int,int> &a, const pair<int,int> &b) { return (a.second < b.second); } 
inline bool sortbysecdesc(const pair<int,int> &a, const pair<int,int> &b) { return (a.second > b.second); } 
inline void swap(int &a,int &b){int temp=a;a=b;b=temp;}
inline void initialise(int A[],int n,int k){for(int i=0;i<n;i++){A[i]=k;}}
inline void vect_input(vector<int>&v,int n){for(int i=0;i<n;i++){int input;cin>>input;v.pb(input);}}
inline int modulo(int a,int b){return (b+(a%b))%b;} 
inline int getascii(char ch){return (int)ch;}
inline ll expo_mod(ll e,ll p){if(p==0)return (1);ll ans=expo_mod(e,p/2);ans=((ans%m)*(ans%m))%m;if(p%2!=0)ans=((e%m)*(ans%m))%m;return ans%m;}
inline ll expo(ll e,ll p){if(p==0)return (1);ll ans=expo(e,p/2);ans=(ans)*(ans);if(p%2!=0)ans=(e)*(ans);return ans;}
inline ll com_wd_m(ll n,ll r,ll m){ll p=1,d=1;if(r==0 or r==n )return(1);if(r==1 )return (n%m);r=min(r,n-r);for(ll i=0;i<r;i++){p=((p%m)*((n%m)-(i%m))%m)%m;p=((p%m)*(expo((i+1),m-2)%m))%m;}return (p%m);}

template<typename T>
void show_vect(vector<T> v){for(int i=0;i<v.size();i++){cout<<v[i]<<" ";}cout<<endl;}
template<typename T>
void vect_input(vector<T>&v,T n){for(int i=0;i<n;i++){cin>>v[i];}}
ll fact(ll n) { return (n==1 || n==0) ? 1: n * fact(n - 1);  } 
ll fact_mod(ll n,ll x) {if(n==x) return 1; return (n==1 || n==0) ? 1: ((n%m) * (fact((n - 1)%m))%m)%m;  } 


//debugging

#define deb(x) cout << #x << " = " << x << endl; //to check the values
#define deb2(x, y) cout << #x << " = " << x << "," << #y << " = " << y << endl;

void A_A()
{
    ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
    #ifndef ONLINE_JUDGE
    freopen("input.in", "r", stdin);
    freopen("output.in", "w", stdout);
    freopen("error.in","w",stderr);
    #endif
}
ll num; 

void solve(){
  ll n,x;
  string s;
  cin>>n>>x;
  cin>>s;
  for(auto i:s){
    if(i=='o') x++;
    if(i=='x' && x-1>=0) x--;
  }
  cout<<x;
}


int main(){
   A_A();
  // tc(t){
    solve();
  // }
  return 0;
}
/*

*/           