#include <bits/stdc++.h>
using namespace std;
const int MAXN = 3010;
const int INF = 0x3f3f3f3f;
int d[MAXN], e[MAXN];
int main() {
  memset(d, INF, sizeof d);
  memset(e, INF, sizeof e);
  int n;
  cin >> n;
  string s;
  cin >> s;
  int at = INF;
  for (int i = 0; i < n; i++) {
    if (s[i] == 'R')
      at = 0;
    else if (s[i] == 'L')
      at = INF;
    d[i] = at;
    if (at < INF) at++;
  }
  at = INF;
  for (int i = n - 1; i >= 0; i--) {
    if (s[i] == 'R')
      at = INF;
    else if (s[i] == 'L')
      at = 0;
    e[i] = at;
    if (at < INF) at++;
  }
  int cont = 0;
  for (int i = 0; i < n; i++) {
    if (d[i] == e[i]) cont++;
  }
  cout << cont << endl;
}
