//#define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
#define rep(i, n) for(int i=0; i<n; ++i)
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
using namespace std;
using ll = int64_t;
using ld = long double;
using P = pair<int, int>;
using vs = vector<string>;
using vi = vector<int>;
using vvi = vector<vi>;
template<class T> using PQ = priority_queue<T>;
template<class T> using PQG = priority_queue<T, vector<T>, greater<T> >;
const int INF = 0xccccccc;
const ll LINF = 0xcccccccccccccccLL;
template<typename T1, typename T2>
inline bool chmax(T1 &a, T2 b) {return a < b && (a = b, true);}
template<typename T1, typename T2>
inline bool chmin(T1 &a, T2 b) {return a > b && (a = b, true);}
template<typename T1, typename T2>
istream &operator>>(istream &is, pair<T1, T2> &p) { return is >> p.first >> p.second;}
template<typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) { return os << p.first << ' ' << p.second;}

//const unsigned int mod = 1000000007;
const unsigned int mod = 998244353;

struct mint {
	unsigned int x;
	mint():x(0) {}
	mint(int64_t x_) {
		int64_t v = int64_t(x_ % mod);
		if(v < 0) v += mod;
		x = (unsigned int)v;
	}
	static mint row(int v) {
		mint v_;
		v_.x = v;
		return v_;
	}
	mint operator-() const { return mint(-x);}
	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) {
		uint64_t z = x;
		z *= a.x;
		x = (unsigned int)(z % mod);
		return *this;
	}
	mint operator+(const mint a) const { return mint(*this) += a;}
	mint operator-(const mint a) const { return mint(*this) -= a;}
	mint operator*(const mint a) const { return mint(*this) *= a;}
	friend bool operator==(const mint &a, const mint &b) {return a.x == b.x;}
	friend bool operator!=(const mint &a, const mint &b) {return a.x != b.x;}
	mint &operator++() {
		x++;
		if(x == mod) x = 0;
		return *this;
	}
	mint &operator--() {
		if(x == 0) x = mod;
		x--;
		return *this;
	}
	mint operator++(int) {
		mint result = *this;
		++*this;
		return result;
	}
	mint operator--(int) {
		mint result = *this;
		--*this;
		return result;
	}
	mint pow(int64_t t) const {
		mint x_ = *this, r = 1;
		while(t) {
			if(t&1) r *= x_;
			x_ *= x_;
			t >>= 1;
		}
		return r;
	}
	//for prime mod
	mint inv() const { return pow(mod-2);}
	mint& operator/=(const mint a) { return *this *= a.inv();}
	mint operator/(const mint a) {return mint(*this) /= a;}
};

istream& operator>>(istream& is, mint& a) { return is >> a.x;}
ostream& operator<<(ostream& os, const mint& a) { return os << a.x;}

//head

int n;
string s;
mint ans(1);
char c[] = "$$$";
int one, two;
const char rgb[] = "RGB";

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	cin >> n;
	cin >> s;
	rep(i, n) ans *= i+1;
	n *= 3;
	rep(i, n) {
		if(c[0] == s[i]) {
			one++;
		}
		else if(c[1] == s[i]) {
			ans *= one--;
			two++;
		}
		else if(c[2] == s[i]) {
			ans *= two--;
		}
		else {
			if(c[0] == '$') {
				c[0] = s[i];
				one++;
			}
			else {
				ans *= one--;
				two++;
				c[1] = s[i];
				rep(x, 3) if(rgb[x] != s[i] and rgb[x] != c[0]) c[2] = rgb[x];
			}
		}
		if(one == 0) c[0] = c[1] = '$';
		if(two == 0) c[1] = c[2] = '$';
		//cout << s[i] << ' ' << P(one, two) << ' ' << c << endl;
	}
	cout << ans << endl;
}

Measured memory_bytes: 3828