#include <bits/stdc++.h>
using namespace std;
#include <atcoder/all>
using namespace atcoder;
#define rep(i, n) for(int i=0;i<(n);++i)
#define rep1(i, n) for(int i=1;i<=(n);i++)
#define ll long long
using mint = modint998244353;
using P = pair<ll,ll>;
using lb = long double;
using T = tuple<ll, ll, ll>;
#ifdef LOCAL
#  include <debug_print.hpp>
#  define dbg(...) debug_print::multi_print(#__VA_ARGS__, __VA_ARGS__)
#else
#  define dbg(...) (static_cast<void>(0))
#endif

int main()
{
    int n, m;
    cin >> n >> m;
    string s;
    cin >> s;
    s = 'x' + s;
    s += 'x';
    n = s.size();
    int ans = 0;
    vector<vector<int>> vs(3);
    for(int i=0;i<n;){
        if(s[i]=='o') ans++;
        int j = i+1;
        while(j<n && s[j]=='-') j++;
        int cnt = 0;
        if(s[i]=='x') cnt++;
        if(s[j]=='x') cnt++;
        vs[cnt].push_back(j-i-1);
        i = j;
    }
    dbg(vs);
    int res = 0;
    for(int i=0;i<3;i++){
        vector<int> odd, even;
        for(int v : vs[i]) {
            if(v==0) continue;
            if(v%2==1) odd.push_back(v);
            else even.push_back(v);
        }
        sort(odd.begin(),odd.end());
        sort(even.begin(),even.end());
        dbg(odd, even);
        if(i==0){
            for(int v : odd){
                int k = v/2;
                if(m>=k) {
                    ans += v;
                    m -= k;
                }
                else{
                    ans += 2*m;
                    m = 0;
                }
            }
            for(int v : even){
                ans += min(v/2, m) * 2;
                m -= min(v/2, m);
            }
        }   
        else if(i==1){
            res+=odd.size();
            for(int v : even){
                ans += min(v/2, m) * 2;
                m -= min(v/2, m);
            }
            for(int v : odd){
                ans += min(v/2, m) * 2;
                m -= min(v/2, m);
            }
        }
        else{
            res += even.size();
            vector<int> nv;
            for(int e : even) nv.push_back(e);
            for(int e : odd) nv.push_back(e);
            sort(nv.rbegin(),nv.rend());
            for(int  e : nv){
                if(m>=1) {
                    m--;
                    ans++;
                    ans += min(m, (e-1)/2)*2;
                    m -= min(m, (e-1)/2);
                }
            }
        }
    }
    dbg(ans);
    ans += min(m, res);
    cout << ans << endl;
    return 0;
}