#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
using namespace std;
const int MAXN = 200000 + 5;
static int w[MAXN], b[MAXN];
static pair<int,int> allPair[MAXN];
int BIT[2*MAXN + 5];
void bit_update(int pos, int M) {
for (pos += 1; pos <= M; pos += pos & -pos)
BIT[pos]++;
}
ll bit_sum(int pos) {
ll s = 0;
for (pos += 1; pos > 0; pos -= pos & -pos)
s += BIT[pos];
return s;
}
ll bit_range(int l, int r) {
return (l > r ? 0LL : bit_sum(r) - (l ? bit_sum(l-1) : 0LL));
}
ll getAns(int n, int k){
int M = 2 * n;
memset(BIT, 0, sizeof(int)*(M+2));
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 += bit_range(allPair[i].first, allPair[i].second);
bit_update(allPair[i].second, M);
}
return curr;
}
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n;
cin >> n;
string s;
cin >> s;
vector<int> w(n), b(n);
vector<pair<int, int>> allPair(n);
vector<int> segTree(8 * n, 0);
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;
}
