#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef pair<ll,ll> P;
typedef vector<ll> VI;
typedef vector<VI> VVI;
#define REP(i,n) for(ll i=0;i<(n);i++)
#define ALL(v) v.begin(),v.end()
template<typename T> bool chmax(T &x, const T &y) {return (x<y)?(x=y,true):false;};
template<typename T> bool chmin(T &x, const T &y) {return (x>y)?(x=y,true):false;};
constexpr ll MOD=998244353;
constexpr ll INF=2e18;

ll power(ll x, ll y){
    x%=MOD;
    ll ret=1;
    while(y){
        if(y&1) ret=ret*x%MOD;
        x=x*x%MOD;
        y>>=1;
    }
    return ret;
}

ll divid(ll x, ll y){
    x%=MOD;
    return x*power(y,MOD-2)%MOD;
}

ll com(ll n, ll k){
    if(n<k)
        return 0;
    ll a=1, b=1;
    for(ll i=1;i<=k;i++){
        a=(a*(n-i+1))%MOD;
        b=(b*i)%MOD;
    }
    return divid(a,b);
}

int main(){
    int n; cin >> n;
    string s; cin >> s;
    int x=0;
    REP(i,n){
        if(s[i]=='A'||s[i]=='B')
            x++;
    }
    cout << com(n,x) << endl;
    return 0;
}