/**
 *   @FileName	a.cpp
 *   @Author	kanpurin
 *   @Created	2021.04.17 02:44:54
**/

#include "bits/stdc++.h" 
using namespace std; 
typedef long long ll;

template< int MOD >
struct mint {
public:
    long long x;
    mint(long long x = 0) :x((x%MOD+MOD)%MOD) {}
    mint(std::string &s) {
        long long z = 0;
        for (int i = 0; i < s.size(); i++) {
            z *= 10;
            z += s[i] - '0';
            z %= MOD;
        }
        this->x = z;
    }
    mint& operator+=(const mint &a) {
        if ((x += a.x) >= MOD) x -= MOD;
        return *this;
    }
    mint& operator-=(const mint &a) {
        if ((x += MOD - a.x) >= MOD) x -= MOD;
        return *this;
    }
    mint& operator*=(const mint &a) {
        (x *= a.x) %= MOD;
        return *this;
    }
    mint& operator/=(const mint &a) {
        long long n = MOD - 2;
        mint u = 1, b = a;
        while (n > 0) {
            if (n & 1) {
                u *= b;
            }
            b *= b;
            n >>= 1;
        }
        return *this *= u;
    }
    mint operator+(const mint &a) const {
        mint res(*this);
        return res += a;
    }
    mint operator-() const {return mint() -= *this; }
    mint operator-(const mint &a) const {
        mint res(*this);
        return res -= a;
    }
    mint operator*(const mint &a) const {
        mint res(*this);
        return res *= a;
    }
    mint operator/(const mint &a) const {
        mint res(*this);
        return res /= a;
    }
    friend std::ostream& operator<<(std::ostream &os, const mint &n) {
        return os << n.x;
    }
    friend std::istream &operator>>(std::istream &is, mint &n) {
        long long x;
        is >> x;
        n = mint(x);
        return is;
    }
    bool operator==(const mint &a) const {
        return this->x == a.x;
    }
    bool operator!=(const mint &a) const {
        return this->x != a.x;
    }
    mint pow(long long k) const {
        mint ret = 1;
        mint p = this->x;
        while (k > 0) {
            if (k & 1) {
                ret *= p;
            }
            p *= p;
            k >>= 1;
        }
        return ret;
    }
};
constexpr int MOD = 998244353;
int main() {
    int n;cin >> n;
    string s;cin >> s;
    vector<vector<int>> cnt(3,vector<int>(n+1,0));
    for (int i = 0; i < n; i++) {
        cnt[0][i+1] = cnt[0][i];
        cnt[1][i+1] = cnt[1][i];
        cnt[2][i+1] = cnt[2][i];
        if (s[i] == 'A') cnt[0][i+1]++;
        if (s[i] == 'B') cnt[1][i+1]++;
        if (s[i] == 'C') cnt[2][i+1]++;
    }
    bool ok = false;
    for (int i = 0; i < n; i++) {
        if (s[i] == 'A' && cnt[2][i] >= 1 && cnt[1][n]-cnt[1][i+1]>=1) {
            ok = true;
            break;
        }
        if (s[i] == 'B' && cnt[0][i] >= 1 && cnt[2][n]-cnt[2][i+1]>=1) {
            ok = true;
            break;
        }
        if (s[i] == 'C' && cnt[1][i] >= 1 && cnt[0][n]-cnt[0][i+1]>=1) {
            ok = true;
            break;
        }
    }
    if (!ok) {
        puts("1");
        return 0;
    }
    mint<MOD> ans = 1;
    for (int i = 1; i < n; i++) {
        ans *= i+1;
    }
    
    
    for (int i = 0; i < 3; i++) {
        for (int j = 1; j < cnt[i][n]; j++) {
            ans /= j+1;
        }
    }
    cout << ans - n << endl;
    return 0;
}