#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, count = 0, b = 0;
  cin >> n;
  string s;
  cin >> s;
  for (int i = 0; i < n; i++) {
    if (s[i] != s[i + 1] && s[i] == 'B') count++;
  }
  cout << count << endl;
  for (int i = 0; i < n; i++) {
    if (s[i] == 'B') {
      b++;
      if (s[i] != s[i + 1]) {
        cout << b << " ";
        b = 0;
      }
    }
  }
  return 0;
}
