#include <bits/stdc++.h>
#define uwu return 0;
using namespace std;
#define fs first
#define sc second
const int SIZE = 2e5 + 5;
string S;
deque <int> pos[2];
vector <int> seg;
int BITree[SIZE];
void modify(int pos, int val){
for (; pos < SIZE; pos += (pos & - pos)){
BITree[pos] += val;
}
return;
}
int query(int pos){
int ret = 0;
for (; pos; pos -= (pos & - pos)){
ret += BITree[pos];
}
return ret;
}
long long eval(int x, int N){
for (int i = 0; i < 2 * N; i++){
BITree[i] = 0;
}
seg.clear();
pos[0].clear();
pos[1].clear();
for (int i = N; i < S.size(); i++){
pos[S[(i + x) % (2 * N)] == 'W'].push_back(i);
}
for (int i = 0; i < N; i++){
seg.push_back(pos[S[(i + x) % (2 * N)] == 'B'].front());
pos[S[(i + x) % (2 * N)] == 'B'].pop_front();
}
long long ans = 0;
for (int i = 0; i < N; i++){
ans += query(seg[i]);
modify(seg[i], 1);
}
return ans;
}
int main(){
cin.tie(0), ios::sync_with_stdio(0);
int N;
cin >> N >> S;
long long ans = 0;
for (int i = 0; i < 2 * N; i++){
ans = max(ans, eval(i, N));
}
cout << ans << '\n';
uwu
}
