#include <iostream>
#include<vector>
#include<algorithm>
#define int long long
using namespace std;
int32_t main() {
ios_base::sync_with_stdio(false); cin.tie(NULL);
int n; cin >> n;
string s; cin >> s;
vector<int> w, b;
for (int i = 0; i < (n + n); ++i)
if (s[i] == 'W')
w.push_back(i);
else
b.push_back(i);
int mx = 0;
for (int k = 0; k < n; ++k) {
int ans = 0;
vector<pair<int, int>> res;
for (int i = 0; i < n; ++i)
res.push_back({ w[i], b[(i + k) % n] });
for (auto x : res)
for (auto y : res)
if (x != y) {
int l1 = x.first, r1 = x.second;
int l2 = y.first, r2 = y.second;
vector<pair<int, int>> a;
a.push_back({ l1, 0 }), a.push_back({ r1, 0 });
a.push_back({ l2, 1 }), a.push_back({ r2, 1 });
sort(a.begin(), a.end());
bool ok = 1;
for (int i = 1; i < 4; ++i)
ok &= (a[i].second != a[i - 1].second);
ans += ok;
}
mx = max(ans / 2, mx);
}
cout << mx;
}
