#include <bits/stdc++.h>

#include <atcoder/all>
using namespace std;

using mint = atcoder::modint998244353;

const int CombMAX = 3000000;
std::vector<mint> fac(CombMAX + 1), finv(CombMAX + 1), inv(CombMAX + 1);

struct Combinationinit {
	Combinationinit() {
		const int MOD = mint::mod();
		fac[0] = fac[1] = 1;
		finv[0] = finv[1] = 1;
		inv[1] = 1;
		for(int i = 2; i <= CombMAX; i++) {
			fac[i] = fac[i - 1] * i;
			inv[i] = MOD - inv[MOD % i] * (MOD / i);
			finv[i] = finv[i - 1] * inv[i];
		}
	}
} Combinationinit_;

int main() {
	int n;
	string s;
	cin >> n >> s;

	int count_a = count(s.begin(), s.end(), 'A');
	int count_b = count(s.begin(), s.end(), 'B');
	int count_c = count(s.begin(), s.end(), 'C');

	bool can_operation = 0, exist_a = 0, exist_ab = 0, exist_b = 0, exist_bc = 0, exist_c = 0, exist_ca = 0;
	for(auto &c : s) {
		if(c == 'A') {
			exist_a = 1;
			if(exist_c) exist_ca = 1;
			if(exist_bc) can_operation = 1;
		}
		if(c == 'B') {
			exist_b = 1;
			if(exist_a) exist_ab = 1;
			if(exist_ca) can_operation = 1;
		}
		if(c == 'C') {
			exist_c = 1;
			if(exist_b) exist_bc = 1;
			if(exist_ab) can_operation = 1;
		}
	}

	if(can_operation) {
		mint res = fac[n] * finv[count_a] * finv[count_b] * finv[count_c] - n;
		cout << res.val() << endl;
	} else
		cout << 1 << endl;
}