#include <bits/stdc++.h>
using namespace std;

const int CombMAX = 100010, mod = 998244353;
long long fac[CombMAX + 1], finv[CombMAX + 1], inv[CombMAX + 1];

struct Combinationinit {
	Combinationinit() {
		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) % mod;
			inv[i] = (mod - (inv[mod % i] * (mod / i)) % mod) % mod;
			finv[i] = (finv[i - 1] * inv[i]) % mod;
		}
	}
} Combinationinit_;

int n, ac, bc, cc;
string s, u;
int main() {
	cin >> n >> s;
	ac = count(s.begin(), s.end(), 'A');
	bc = count(s.begin(), s.end(), 'B');
	cc = count(s.begin(), s.end(), 'C');
	//A,B,C全てが存在しない場合
	if(min({ac, bc, cc}) == 0) {
		cout << "1\n";
		return 0;
	}

	int cp = s.find('C');
	rotate(s.begin(), s.begin() + cp, s.end());
	string u = s;
	sort(u.rbegin(), u.rend());
	//C..CB..BA..Aであり、操作が不可能な場合
	if(s == u) {
		cout << "1\n";
		return 0;
	}

	long long res = ((((fac[n] * finv[ac]) % mod * finv[bc]) % mod * finv[cc]) % mod - n) % mod;
	if(res < 0) res += mod;

	cout << res << '\n';

	return 0;
}