#include <bits/stdc++.h>
using namespace std;
void upd(int ind,int val,vector<int>& tour,int ofs){
ind+=ofs;
tour[ind]+=val;
while (ind>1){
ind/=2;
tour[ind]=tour[ind*2]+tour[ind*2+1];
}
}
int que(int l,int r,int l2,int r2,int ind,vector<int>& tour){
if (r<l2 || r2<l){
return 0;
}
if (l<=l2 && r2<=r){
return tour[ind];
}
return que(l,r,l2,(l2+r2)/2,ind*2,tour)+que(l,r,(l2+r2)/2+1,r2,ind*2+1,tour);
}
int main(){
//ios_base::sync_with_stdio(false);
//cin.tie(NULL);
int n;
string s;
cin >> n >> s;
int isp=0;
int ofs=1;
while (ofs<n*4){
ofs*=2;
}
vector<int> w={};
vector<int> b={};
for (int i=0;i<n*2;i++){
if (s[i]=='W'){
w.push_back(i);
}
else {
b.push_back(i);
}
}
for (int k=max(0,n/2-5);k<min(n,n/2+5);k++){
// cout << k << "\n";
int ind1=0;
int ind2=k;
vector<pair<int,int>> lis(n,pair<int,int>{});
for (int i=0;i<n;i++){
lis[i].first=w[ind1];
lis[i].second=b[ind2];
if (lis[i].second<lis[i].first){
swap(lis[i].first,lis[i].second);
}
ind1++;
ind1%=n;
ind2++;
ind2%=n;
}
sort(lis.begin(),lis.end());
int rje=0;
vector<int> tour(ofs*2,0);
for (int i=0;i<n;i++){
int a=lis[i].first;
int b=lis[i].second;
// cout << a << " " << b << "\n";
rje+=que(a,b,0,ofs-1,1,tour);
// cout << rje << "\n";
upd(b,1,tour,ofs);
// cout << "a\n";
}
isp=max(isp,rje);
// cout << k << " " << rje << "\n";
}
cout << isp << "\n";
}
