#include <bits/stdc++.h>
#pragma GCC optimize("unroll-loops")
using namespace std;
using std::cout;
using std::cin;
using std::endl;
using ll=long long;
using ld=long double;
const ll ILL=2167167167167167167;
const int INF=2100000000;
const int mod=998244353;
#define rep(i,a,b) for (int i=(int)(a);i<(int)(b);i++)
#define all(p) p.begin(),p.end()
template<class T> using _pq = priority_queue<T, vector<T>, greater<T>>;
template<class T> ll LB(vector<T> &v,T a){return lower_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> ll UB(vector<T> &v,T a){return upper_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> bool chmin(T &a,const T &b){if(a>b){a=b;return 1;}else return 0;}
template<class T> bool chmax(T &a,const T &b){if(a<b){a=b;return 1;}else return 0;}
template<class T> void So(vector<T> &v) {sort(v.begin(),v.end());}
template<class T> void Sore(vector<T> &v) {sort(v.begin(),v.end(),[](T x,T y){return x>y;});}
void yneos(bool a,bool upp=0){if(a) cout<<(upp?"YES\n":"Yes\n"); else cout<<(upp?"NO\n":"No\n");}
template<class T> void vec_out(vector<T> &p,int ty=0){
if(ty==2){cout<<'{';for(int i=0;i<(int)p.size();i++){if(i){cout<<",";}cout<<'"'<<p[i]<<'"';}cout<<"}\n";}
else{if(ty==1){cout<<p.size()<<"\n";}for(int i=0;i<(int)(p.size());i++){if(i) cout<<" ";cout<<p[i];}cout<<"\n";}}
template<class T> T vec_min(vector<T> &a){assert(!a.empty());T ans=a[0];for(auto &x:a) chmin(ans,x);return ans;}
template<class T> T vec_max(vector<T> &a){assert(!a.empty());T ans=a[0];for(auto &x:a) chmax(ans,x);return ans;}
template<class T> T vec_sum(vector<T> &a){assert(!a.empty());T ans=a[0]-a[0];for(auto &x:a) ans+=x;return ans;}
int pop_count(long long a){int res=0;while(a){res+=(a&1),a>>=1;}return res;}

void solve();
// oddloop
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    
    int t=1;
    //cin>>t;
    rep(i,0,t) solve();
}

void solve(){
    int N,M;
    cin>>N>>M;
    string S;
    cin>>S;
    int ans=0;
    vector<int> p1,p2;
    int X1=0,X2=0;
    int l=0,r=0;
    while(l=r,l!=N-1){
        r++;
        while(S[r]=='-') r++;
        int len=r-l-1;
        int tmp=0;
        if(S[l]=='o') tmp++;
        if(S[r]=='o') tmp++;
        if(len<=0){
            continue;
        }
        if(tmp==0){
            if(len%2==0) len--,X1++;
            p1.push_back(len/2);
        }
        else if(1==(len&1)&&tmp==2){
            if(len==1) ans++;
            else p2.push_back(len/2-1);
        }
        else{
            X2+=len/2;
            X1+=len%2;
        }
    }
    So(p2);
    Sore(p1);
    vector<int> q;
    for(auto x:p2){
        rep(i,0,x) q.push_back(2);
        q.push_back(3);
    }
    rep(i,0,X2) q.push_back(2);
    for(auto x:p1){
        q.push_back(1);
        rep(i,0,x) q.push_back(2);
    }
    rep(i,0,X1) q.push_back(1);
    while((int)(q.size())<M) q.push_back(0);
    q.resize(M);
    if(!q.empty()) ans+=vec_sum(q);
    for(auto c:S) if(c=='o') ans++;
    cout<<ans<<"\n";
}