#include<bits/stdc++.h>
using namespace std;
int main(){
int n, res, m;
vector<int> r;
string s;
cin >> n;
cin >>s;
for(int i = 0; i < n; ++i){
if(s[i] == 'B'){
m = 0;
while(s[i] == 'B'){
m++;
i++;
}
r.push_back(m);
}
}
cout << r.size() << endl;
for(int i = 0; i < r.size(); ++i) cout << r[i] << " ";
}
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