#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#pragma GCC target("avx,avx2,fma")
#define ll long long
#define pb push_back
#define MAXN 200000
using namespace std;
int w[MAXN], b[MAXN];
pair<int, int> allPair[MAXN];
int segTree[8 * MAXN];
void update(int curr, int pos, int l, int r){
segTree[curr]++;
if (l == r) return;
int mid = (r - l) / 2 + l;
if (pos <= mid){
update(curr * 2 + 1, pos, l, mid);
}
else{
update(curr * 2 + 2, pos, mid + 1, r);
}
}
ll getCount(int curr, int l, int r, int findL, int findR){
if (l >= findL && r <= findR) return segTree[curr];
int mid = (r - l) / 2 + l;
ll ans = 0;
if (findL <= mid){
ans += getCount(curr * 2 + 1, l, mid, findL, findR);
}
if (findR > mid){
ans += getCount(curr * 2 + 2, mid + 1, r, findL, findR);
}
return ans;
}
ll getAns(int n, int k){
for (int i = 0; i < 8 * n; i++){
segTree[i] = 0;
}
ll curr = 0;
for (int i = 0; i < n; i++){
int wPos = w[i], bPos = b[(i + k) % n];
allPair[i] = {min(wPos, bPos), max(wPos, bPos)};
}
sort(allPair, allPair + n);
for (int i = 0; i < n; i++){
curr += getCount(0, 0, 2 * n - 1, allPair[i].first, allPair[i].second);
update(0, allPair[i].second, 0, 2 * n - 1);
}
return curr;
}
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n;
cin >> n;
string s;
cin >> s;
int curW = 0, curB = 0;
for (int i = 0; i < 2 * n; i++){
if (s[i] == 'W'){
w[curW++] = i;
}
else{
b[curB++] = i;
}
}
ll ans = 0;
int left = 0, right = n - 1, mid;
while(left <= right){
mid = (right - left) / 2 + left;
ll curr = getAns(n, mid);
ll prev = 0;
if (mid - 1 >= 0){
prev = getAns(n, mid - 1);
}
ans = max(ans, curr);
if (curr > prev){
left = mid + 1;
}
else{
right = mid - 1;
}
}
ans = max(ans, getAns(n, 0));
ans = max(ans, getAns(n, n - 1));
cout << ans << "\n";
return 0;
}
