#include <algorithm>
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
int N;
cin >> N;
vector<int> W, B;
W.reserve(N);
B.reserve(N);
for (int i = 0; i < 2 * N; ++i) {
char c;
cin >> c;
(c == 'W' ? W : B).push_back(i);
}
vector<ll> coeff(N);
auto add = [&](int l, int r, int x) {
while (l < 0) {
l += N;
r += N;
}
while (l >= N) {
l -= N;
r -= N;
}
if (r < N) {
coeff[l] += x;
coeff[r] -= x;
} else {
coeff[l] += x;
coeff[0] += x;
coeff[r - N] -= x;
}
};
for (int i = 0, a = 0, b = 0, c = 0; i < N; ++i) {
while (a < N and W[i] - B[a] > N) a += 1;
while (b < N and B[b] < W[i]) b += 1;
while (c < N and B[c] - W[i] < N) c += 1;
add(0 - i, a - i, 2 * N);
add(c - i, N - i, 2 * N);
add(0 - i, a - i, -W[i]);
add(a - i, b - i, +W[i]);
add(b - i, c - i, -W[i]);
add(c - i, N - i, +W[i]);
}
for (int i = 0, a = 0, b = 0, c = 0; i < N; ++i) {
while (a < N and B[i] - W[a] >= N) a += 1;
while (b < N and W[b] <= B[i]) b += 1;
while (c < N and W[c] - B[i] <= N) c += 1;
add(i - a + 1, i - 0 + 1, -B[i]);
add(i - b + 1, i - a + 1, +B[i]);
add(i - c + 1, i - b + 1, -B[i]);
add(i - N + 1, i - c + 1, +B[i]);
}
for (int i = 1; i < N; ++i) {
coeff[i] += coeff[i - 1];
}
cout << (*max_element(begin(coeff), end(coeff)) - N) / 2 << '\n';
return 0;
}
