#include <bits/stdc++.h>
using namespace std;
const double PI = acos(-1);
const double eps = 1e-9;
const int inf = 2000000000;
const long long infLL = 1000000000000000000;
int dx[] = {0, 0, +1, -1};
int dy[] = {+1, -1, 0, 0};
template <typename first, typename second>
ostream &operator<<(ostream &os, const pair<first, second> &p) {
  return os << "(" << p.first << ", " << p.second << ")";
}
template <typename T>
ostream &operator<<(ostream &os, const vector<T> &v) {
  os << "{";
  for (auto it = v.begin(); it != v.end(); ++it) {
    if (it != v.begin()) os << ", ";
    os << *it;
  }
  return os << "}";
}
template <typename T>
ostream &operator<<(ostream &os, const set<T> &v) {
  os << "[";
  for (auto it = v.begin(); it != v.end(); ++it) {
    if (it != v.begin()) os << ", ";
    os << *it;
  }
  return os << "]";
}
template <typename T>
ostream &operator<<(ostream &os, const multiset<T> &v) {
  os << "[";
  for (auto it = v.begin(); it != v.end(); ++it) {
    if (it != v.begin()) os << ", ";
    os << *it;
  }
  return os << "]";
}
template <typename first, typename second>
ostream &operator<<(ostream &os, const map<first, second> &v) {
  os << "[";
  for (auto it = v.begin(); it != v.end(); ++it) {
    if (it != v.begin()) os << ", ";
    os << it->first << " = " << it->second;
  }
  return os << "]";
}
void faltu() { cerr << '\n'; }
template <typename T>
void faltu(T a[], int n) {
  for (int i = 0; i < n; ++i) cerr << a[i] << ' ';
  cerr << '\n';
}
template <typename T, typename... hello>
void faltu(T arg, const hello &...rest) {
  cerr << arg << ' ';
  faltu(rest...);
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  ;
  int n;
  cin >> n;
  string s;
  cin >> s;
  int ans = 0;
  int p = 0, f, l;
  for (int i = 0; i < n; i++) {
    f = i;
    if (i == n - 1 && s[i] == '.') {
      cout << n << '\n';
      return 0;
    }
    if (s[i] == '.')
      p++;
    else if (s[i] == 'L')
      break;
    else {
      ans += p;
      break;
    }
  }
  p = 0;
  for (int i = n - 1; i >= 0; i--) {
    l = i;
    if (s[i] == '.')
      p++;
    else if (s[i] == 'R')
      break;
    else {
      ans += p;
      break;
    }
  }
  char prev;
  prev = s[f];
  p = 0;
  for (int i = f + 1; i <= l; i++) {
    if (s[i] == '.')
      ++p;
    else {
      if (prev == 'L' && s[i] == 'R') ans += p;
      if (prev == 'R' && s[i] == 'L')
        if (p % 2 == 1) ans++;
      p = 0;
      prev = s[i];
    }
  }
  cout << ans << '\n';
  return 0;
}
