#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;
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();
for (int j = 0; j < n; j++)
{
int v = W[j];
int u = B[(j + i) % n];
seg.push_back({min(v, u), max(v, u)});
}
int tmp = 0;
for (int j = 0; j < n; j++)
{
for (int k = j + 1; k < n; k++)
{
auto [l1, r1] = seg[j];
auto [l2, r2] = seg[k];
if ((l1 <= l2 && l2 <= r1) ^ (l1 <= r2 && r2 <= r1))
tmp++;
}
}
ans = max(ans, tmp);
}
cout << ans << endl;
}
