#include <iostream>
#include <string>
#include <vector>

using namespace std;
typedef long long ll;
ll mod = 998244353,f[200010];
ll pw(ll a,ll x){
    ll ret = 1;
    while(x){
        if(x&1) (ret *= a) %= mod;
        (a *= a) %= mod; x /= 2;
    }
    return ret;
}

int main(){
    ll i,n; string s;
    cin >> n >> s;
    int a = 0,ab = 0,abc = 0,b = 0,bc = 0,bca = 0,c = 0,ca = 0,cab = 0;
    vector<ll> cnt(3);
    for(i=0;i<s.size();i++){
        cnt[s[i] - 'A']++;
        if(s[i]=='A'){
            a = 1;
            if(bc) bca = 1;
            if(c) ca = 1;
        }
        if(s[i]=='B'){
            b = 1;
            if(a) ab = 1;
            if(ca) cab = 1;
        }
        if(s[i]=='C'){
            c = 1;
            if(ab) abc = 1;
            if(b) bc = 1;
        }
    }
    if(!abc && !bca && !cab){
        cout << 1 << endl;
        return 0;
    }
    f[0] = 1;
    for(i=1;i<=n;i++) f[i] = (f[i - 1]*i)%mod;
    ll ans = f[n];
    for(i=0;i<3;i++) (ans *= pw(f[cnt[i]],mod - 2)) %= mod;
    (ans += mod - n) %= mod;
    cout << ans << endl;
}