#include <iostream>
#include <algorithm>
#include <vector>
#define forn(i,n) for(int i=0;i<(int)n;++i)
#define fori(i,a,n) for(int i=a;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;
}
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
#ifdef LOCAL
freopen("input.in", "r", stdin);
#endif
int n, ans = 0;
string s;
cin>>n>>s;
vector<int> a, b, ps(n);
forn(i,2*n){
if(s[i] == 'W') a.push_back(i);
else b.push_back(i);
}
forn(i,n){
ps[i] = i;
}
do{
int cnt = 0;
vector<pair<int,int>> rs;
forn(i,n){
int x = a[i], y = b[ps[i]];
if(x > y) swap(x, y);
for(auto [u, v] : rs){
int check = 0;
if(u > x && u < y) check |= 1;
else check |= 2;
if(v > x && v < y) check |= 1;
else check |= 2;
if(check == 3) ++cnt;
//~ DBG(cnt);
}
rs.push_back({x, y});
//~ DBG2(x, y);
}
//~ DBG(ans);
//~ DBG("=============");
ans = max(ans, cnt);
} while(next_permutation(ALL(ps)));
cout<<ans<<"\n";
return 0;
}
