/* -*- coding: utf-8 -*-
 *
 * 2553.cc:  No.2553 Holidays - yukicoder
 */

#include<cstdio>
#include<vector>
#include<queue>
#include<algorithm>
#include<utility>
 
using namespace std;

/* constant */

const int MAX_N = 100000;

/* typedef */

using pii = pair<int,int>;
using vpii = vector<pii>;
using qpii = queue<pii>;

/* global variables */

char s[MAX_N + 4];

/* subroutines */

bool cmppii(const pii &a, const pii &b) {
  return a.second - a.first > b.second - b.first;
}

/* main */

int main() {
  int n, m;
  scanf("%d%d%s", &n, &m, s);

  qpii q0, q1;
  vpii es;
  for (int i = 0; i < n;) {
    while (i < n && s[i] != '-') i++;
    if (i >= n) break;

    int j= i;
    while (i < n && s[i] == '-') i++;

    bool lf = (j > 0 && s[j - 1] == 'o');
    bool rf = (i < n && s[i] == 'o');
    if (lf && rf) {
      if ((i - j) & 1) q0.push({j, i});
      else q1.push({j, i});
    }
    else if (lf || rf) q1.push({j, i});
    else es.push_back({j, i});
  }

  while (m > 0 && ! q0.empty()) {
    auto [l, r] = q0.front(); q0.pop();
    for (int i = l + 1; m > 0 && i < r; i += 2)
      s[i] = 'o', m--;
  }

  while (m > 0 && ! q1.empty()) {
    auto [l, r] = q1.front(); q1.pop();
    if (l > 0 && s[l - 1] == 'o')
      for (int i = l + 1; m > 0 && i < r; i += 2)
	s[i] = 'o', m--;
    else
      for (int i = r - 2; m > 0 && i >= l; i -= 2)
	s[i] = 'o', m--;
  }

  sort(es.begin(), es.end(), cmppii);
  for (auto [l, r]: es) {
    if (m <= 0) break;

    if (r - l >= 3)
      for (int i = l; i < r; i += 2)
	s[i] = 'o', m--;
  }

  for (int i = 1; i + 1 < n; i++)
    if (s[i] == '-' && s[i - 1] == 'o' && s[i + 1] == 'o')
      s[i] = 'o';

  for (int i = 0; m > 0 && i < n; i++)
    if (s[i] == '-') s[i] = 'o', m--;
  
  int cnt = 0;
  for (int i = 0; i < n; i++)
    if (s[i] == 'o') cnt++;
  
  printf("%d\n", cnt);
  
  return 0;
}