#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define ll long long
#define ld long double
#define ull unsigned long long
#define ff first
#define ss second
#define pii pair<int,int>
#define pll pair<long long, long long>
#define vi vector<int>
#define vl vector<long long>
#define pb push_back
#define rep(i, b) for(int i = 0; i < (b); ++i)
#define rep2(i,a,b) for(int i = a; i <= (b); ++i)
#define rep3(i,a,b,c) for(int i = a; i <= (b); i+=c)
#define count_bits(x) __builtin_popcountll((x))
#define all(x) (x).begin(),(x).end()
#define siz(x) (int)(x).size()
#define forall(it,x) for(auto& it:(x))
using namespace __gnu_pbds;
using namespace std;
typedef tree<int, null_type, less<int>, rb_tree_tag,tree_order_statistics_node_update> ordered_set;
//mt19937 mt;void random_start(){mt.seed(chrono::time_point_cast<chrono::milliseconds>(chrono::high_resolution_clock::now()).time_since_epoch().count());}
//ll los(ll a, ll b) {return a + (mt() % (b-a+1));}
const int INF = 1e9+50;
const ll INF_L = 1e18+40;
const ll MOD = 1e9+7;
string move(string s, int x)
{
string s2;
int n = siz(s);
for(int i = n-x; i < n; i++) s2 += s[i];
rep(i,n-x) s2 += s[i];
return s2;
}
ll solve(vi& x, vi& y)
{
if(siz(x) > siz(y))
{
swap(x,y);
reverse(all(x));
reverse(all(y));
}
ll cnt0 = 0;
ll cnt1 = 0;
ll cnt20 = 0;
ll cnt21 = 0;
ll cnty0 = 0;
ll cnty1 = 0;
forall(it,x) if(it == 0) cnt0++; else cnt1++;
forall(it,y) if(it == 0) cnt20++; else cnt21++;
forall(it,y) if(it == 0) cnty0++; else cnty1++;
ll ans = siz(x)+(cnt0*(cnt0-1))/2+(cnt1*(cnt1-1))/2;
int pref0 = -1;
int pref1 = siz(y)+1;
int in0 = cnty0-cnt1;
int in1 = cnty1-cnt0;
cnty0 = cnty0-cnt1;
cnty1 = cnt0+1;
ans += cnty0*(cnty0-1)/2;
rep(i,siz(y))
{
if(y[i] == 0) cnty0--;
else cnty1--;
if(cnty0 == 0 && y[i] == 0)
{
cnty0--;
pref0 = i;
}
if(cnty1 == 0 && y[i] == 1)
{
cnty1--;
pref1 = i;
}
}
if(pref0 > pref1) return -1;
int cur_seg = 0;
rep(i,siz(y))
{
if(y[i] == 0)
{
if(i <= pref0) cur_seg++;
else ans += cur_seg;
}
else
{
if(i >= pref1) cur_seg--;
else ans += cur_seg;
}
}
int up1 = cnt1;
int down0 = cnt20-in1;
int cur_ptr = -1;
rep(i,siz(x))
{
if(x[i] == 1)
{
up1--;
continue;
}
cur_ptr++;
while(y[cur_ptr] == 0)
{
if(cur_ptr > pref0) down0--;
cur_ptr++;
}
ans += min(up1,down0);
}
int up0 = cnt0;
int down1 = cnt21-in0;
cur_ptr = -1;
rep(i,siz(x))
{
if(x[i] == 0)
{
up0--;
continue;
}
cur_ptr++;
while(y[cur_ptr] == 1 || cur_ptr <= pref0)
{
if(cur_ptr < pref1 && y[cur_ptr] == 1) down1--;
cur_ptr++;
}
ans += min(up0,down1);
}
return ans;
}
int n;
string s;
ll ans = 0;
ll check_ind(int k)
{
vi x,y;
rep2(j,1,k-1) if(s[j] == 'W') x.pb(0); else x.pb(1);
rep2(j,k+1,n-1) if(s[j] == 'W') y.pb(0); else y.pb(1);
ll ans2 = solve(x,y);
ans = max(ans,ans2);
return ans2;
}
bool check_dir(vi& V, int ind)
{
bool dir = 0;
ll val1 = check_ind(V[ind]);
rep2(ind2,ind+1,siz(V)-1)
{
ll val2 = check_ind(V[ind2]);
if(val2 == val1) continue;
if(val2 > val1) dir = 1;
break;
}
return dir;
}
int main()
{
ios_base::sync_with_stdio(0);cin.tie(0);cerr.tie(0);
//random_start();
cin >> n >> s;
n *= 2;
int d = 0;
rep(i,n) if(s[i] == 'W') d = n-i;
s = move(s,d);
int mid = n/2;
vi V;
rep(i,n) if(s[i] == 'B') V.pb(i);
int mid_point = 0;
rep(i,siz(V)) if(V[i] < n/2) mid_point = i;
int l = 0;
int r = mid_point;
int l_bor = mid_point+1;
while(l <= r)
{
int mid = (l+r)/2;
if(check_ind(V[mid]) != -1)
{
l_bor = mid;
r = mid-1;
}
else
{
l = mid+1;
}
}
l = mid_point+1;
r = siz(V)-1;
int r_bor = mid_point;
while(l <= r)
{
int mid = (l+r)/2;
if(check_ind(V[mid]) != -1)
{
r_bor = mid;
l = mid+1;
}
else
{
r = mid-1;
}
}
l = l_bor;
r = r_bor;
while(l <= r)
{
int mid = (l+r)/2;
if(check_dir(V,mid))
{
l = mid+1;
}
else
{
r = mid-1;
}
}
cout << ans << '\n';
}
