#include <bits/stdc++.h>
using namespace std;
using lint = long long;
const lint mod = 1e9 + 7;
#define all(x) (x).begin(), (x).end()
#define bitcount(n) __builtin_popcountl((lint)(n))
#define fcout cout << fixed << setprecision(15)
#define highest(x) (63 - __builtin_clzl(x))
template<class T> inline void YES(T condition){ if(condition) cout << "YES" << endl; else cout << "NO" << endl; }
template<class T> inline void Yes(T condition){ if(condition) cout << "Yes" << endl; else cout << "No" << endl; }
template<class T> inline void assert_NO(T condition){ if(!condition){ cout << "NO" << endl; exit(0); } }
template<class T> inline void assert_No(T condition){ if(!condition){ cout << "No" << endl; exit(0); } }
template<class T> inline void assert_minus_1(T condition){ if(!condition){ cout << -1 << endl; exit(0); } }
lint power(lint base, lint exponent, lint module){ if(exponent % 2){ return power(base, exponent - 1, module) * base % module; }else if(exponent){ lint root_ans = power(base, exponent / 2, module); return root_ans * root_ans % module; }else{ return 1; }}
struct position{ int y, x; }; position mv[4] = {{0, -1}, {1, 0}, {0, 1}, {-1, 0}}; // double euclidean(position first, position second){ return sqrt((second.x - first.x) * (second.x - first.x) + (second.y - first.y) * (second.y - first.y)); }
template<class T, class U> string to_string(pair<T, U> x){ return to_string(x.first) + "," + to_string(x.second); } string to_string(string x){ return x; }
template<class itr> void array_output(itr start, itr goal){ string ans; for(auto i = start; i != goal; i++) ans += to_string(*i) + " "; if(!ans.empty()) ans.pop_back(); cout << ans << endl; }
template<class itr> void cins(itr first, itr last){ for(auto i = first; i != last; i++){ cin >> (*i); } }
template<class T> T gcd_calc(T a, T b){ if(b){ return gcd_calc(b, a % b); }else{ return a; }}
template<class T> T gcd(T a, T b){ if(a < b) swap(a, b); return gcd_calc(a, b); }
template<class T> T lcm(T a, T b){ return a / gcd(a, b) * b; }
struct combination{ vector<lint> fact, inv; combination(int sz) : fact(sz + 1), inv(sz + 1){ fact[0] = 1; for(int i = 1; i <= sz; i++){ fact[i] = fact[i - 1] * i % mod; } inv[sz] = power(fact[sz], mod - 2, mod); for(int i = sz - 1; i >= 0; i--){ inv[i] = inv[i + 1] * (i + 1) % mod; } } lint C(int p, int q) const{ if(q < 0 || p < q) return 0; return (fact[p] * inv[q] % mod * inv[p - q] % mod); } };
template<class itr> bool next_sequence(itr first, itr last, int max_bound){ itr now = last; while(now != first){ now--; (*now)++; if((*now) == max_bound){ (*now) = 0; }else{ return true; } } return false; }
template<class T> bool chmax(T &a, const T &b){ if(a < b){ a = b; return 1; } return 0; }
template<class T> bool chmin(T &a, const T &b){ if(b < a){ a = b; return 1; } return 0; }
inline int at(int x, int k){ return (x >> k) & 1; }
random_device rnd;
#define rep(i, n) for(int i = 0; i < (n); i++)
#define rep2(i, l, n) for(int i = int(l); i < (n); i++)
#define repr(i, n) for(int i = int(n) - 1; i >= 0; i--)

int main(){
    string a;
    cin >> a;
    lint sz = a.size(), ans = sz * (sz + 1) / 2;
    for(char i = 'a'; i <= 'z'; i++){
        sz = count(all(a), i);
        ans -= sz * (sz + 1) / 2;
    }
    cout << ans + 1 << endl;
}

#include<iostream>
#include<algorithm>
#include<vector>
#include<string>
#include<utility>
#include<map>
#include<set>
#include<queue>
#include<stack>
#include<functional>
#include<math.h>
using namespace std;
#define N (1000000000+7)
#define INF 1e16
typedef long long ll;
typedef pair<ll,ll> P;
 





int main(void){
    ll n;
    string s;
    cin>>n;
    cin>>s;
    ll ans = 1;
    ll num = 0;
    for(ll i=0;i<2*n;i++){
        if((2*n-1-i)%2==1){
            if(s[i]=='B')num++;
            else{
                ans = ans*num;
                ans = ans%N;
                num--;
            }
        }
        else{
            if(s[i]=='W')num++;
            else{
                ans = ans*num;
                ans = ans%N;
                num--;
            }
        }
    }
    if(num!=0){
        cout<<0<<endl;
        return 0;
    }
    for(ll i=1;i<=n;i++){
        ans = ans*i;
        ans = ans%N;
    }
    cout<<ans<<endl;
    return 0;
}

