#include <bits/stdc++.h>
using namespace std;
#define int long long int
typedef pair <int, int> pii;
const int MAXN = 2e5 + 10;
vector <int> W;
vector <int> B;
vector <pii> seg;
struct Fenwick {
int node[MAXN];
void update(int n, int ind, int val)
{
for (; ind <= n; ind += ind & -ind)
node[ind] += val;
}
int get(int ind)
{
int res = 0;
for (; ind; ind -= ind & -ind)
res += node[ind];
return res;
}
int get(int l, int r)
{
return get(r) - get(l - 1);
}
} Fen;
bool cmp(pii x, pii y)
{
return x.second < y.second;
}
signed main()
{
int n, ans = 0;
cin >> n;
for (int i = 1; i <= 2 * n; i++)
{
char c;
cin >> c;
if (c == 'W')
W.push_back(i);
else
B.push_back(i);
}
for (int i = 1; i <= n; i++)
{
seg.clear();
memset(Fen.node, 0, sizeof(Fen.node));
for (int j = 0; j < n; j++)
{
int v = B[j];
int u = W[(j + i) % n];
seg.push_back({min(v, u), max(v, u)});
Fen.update(2 * n, min(v, u), +1);
}
sort(seg.begin(), seg.end(), cmp);
int tmp = 0;
for (int j = 0; j < n; j++)
{
Fen.update(2 * n, seg[j].first, -1);
tmp += Fen.get(seg[j].first, seg[j].second);
}
ans = max(ans, tmp);
}
cout << ans << endl;
}
