#include <iostream>
#include <algorithm>
#include <vector>
#define forn(i,n) for(int i=0;i<(int)n;++i)
#define DBG(a) cerr<<#a<<" = "<<a<<endl
#define DBGA(a) cerr<<#a<<" = "<<a<<", ";
#define DBG2(a,b) do{DBGA(a)DBG(b);}while(0)
#define DBG3(a,b,c) do{DBGA(a)DBGA(b)DBG(c);}while(0)
#define DBG4(a,b,c,d) do{DBGA(a)DBGA(b)DBGA(c)DBG(d);}while(0)
#define SZ(v) (int)v.size()
#define ALL(v) v.begin(),v.end()
using namespace std;
template<typename T>
ostream &operator<<(ostream &os, vector<T> &v){
os<<"[";
forn(i,SZ(v)){
if(i) os<<", ";
os<<v[i];
}
os<<"]";
return os;
}
typedef long long ll;
struct ST{
int n;
vector<int> st;
ST(int _n){
n = 1<<(32-__builtin_clz(_n-1));
st.resize(2*n-1);
}
void update(int i, int x){
i += n-1;
st[i] += x;
while(i){
i = (i-1)/2;
st[i] = st[2*i+1]+st[2*i+2];
}
}
int query(int ql, int qr, int l, int r, int i){
if(l>=qr||r<=ql) return 0;
if(l>=ql&&r<=qr) return st[i];
int m=(l+r)/2;
return query(ql,qr,l,m,2*i+1)+query(ql,qr,m,r,2*i+2);
}
int query(int l, int r){
return query(l,r,0,n,0);
}
};
ll check(int k, vector<int> a, vector<int> b){
int n = SZ(a);
rotate(b.begin(), b.begin()+k, b.end());
vector<pair<int,int>> rs;
forn(i,n){
int l = a[i], r = b[i];
if(l > r) swap(l, r);
rs.push_back({l, r});
rs.push_back({r, l});
}
sort(ALL(rs));
ll ret = 0;
ST mono(2*n);
for(auto x: rs){
if(x.first < x.second){
ret += mono.query(x.first, x.second);
mono.update(x.second, +1);
} else{
mono.update(x.first, -1);
}
}
return ret;
}
void solve(){
int n;
string s;
cin>>n>>s;
vector<int> a, b;
forn(i,2*n){
if(s[i] == 'W') a.push_back(i);
else b.push_back(i);
}
int l=0, r=n+1;
while(l+1<r){
int m = (l+r)/2;
ll x = check(m-1, a, b), y = check(m, a, b);
if(y > x){
l = m;
} else{
r = m; // ???
}
}
ll ans = check(l, a, b);
cout<<ans<<"\n";
}
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
#ifdef LOCAL
freopen("input.in", "r", stdin);
int tcs;
cin>>tcs;
while(tcs--)
#endif
solve();
return 0;
}
