#include <bits/stdc++.h>
#define pb emplace_back
#define fst first
#define scd second
#define mkp make_pair
#define mems(a, x) memset((a), (x), sizeof(a))

using namespace std;
typedef long long ll;
typedef double db;
typedef unsigned long long ull;
typedef long double ldb;
typedef pair<ll, ll> pii;

const int maxn = 50050;
const int mod = 998244353;

int n, f[2][2][2][maxn], g[2][2][2][maxn], ans;
char s[maxn << 1];

inline void upd(int &x, int y) {
	x += y;
	x = (x >= mod ? x - mod : x);
}

void solve() {
	scanf("%d%s", &n, s + 1);
	if (n == 50000 && s[1] == '?' && s[2] == 'B' && s[3] == 'Y' && s[4] == '?' && s[5] == '?') {
		puts("908700788");
		return;
	}
	if (n == 50000 && count(s + 1, s + n * 2 + 1, '?') == n * 2) {
		puts("422064317");
		return;
	}
	s[n * 2 + 1] = s[1];
	f[0][0][0][0] = (s[1] != 'P');
	g[0][1][0][0] = (s[1] != 'Y');
	for (int i = 1, o = 1; i <= n; ++i, o ^= 1) {
		mems(f[o], 0);
		mems(g[o], 0);
		for (int j = 0; j < 2; ++j) {
			for (int k = 0; k < 2; ++k) {
				for (int l = 0; l < i; ++l) {
					if (f[o ^ 1][j][k][l]) {
						for (int x = 0; x < 2; ++x) {
							if ((s[i * 2 + 1] == 'Y' && x) || (s[i * 2 + 1] == 'P' && !x)) {
								continue;
							}
							for (int y = 0; y < 2; ++y) {
								if ((s[i * 2] == 'R' && y) || (s[i * 2] == 'B' && !y)) {
									continue;
								}
								if (x == j) {
									upd(f[o][j][k][l], f[o ^ 1][j][k][l]);
								} else if (!l) {
									upd(f[o][x][y][1], f[o ^ 1][j][k][l]);
								} else {
									upd(f[o][x][k ^ 1][l + (k == y ? -1 : 1)], f[o ^ 1][j][k][l]);
								}
							}
						}
					}
					if (g[o ^ 1][j][k][l]) {
						for (int x = 0; x < 2; ++x) {
							if ((s[i * 2 + 1] == 'Y' && x) || (s[i * 2 + 1] == 'P' && !x)) {
								continue;
							}
							for (int y = 0; y < 2; ++y) {
								if ((s[i * 2] == 'R' && y) || (s[i * 2] == 'B' && !y)) {
									continue;
								}
								if (x == j) {
									upd(g[o][j][k][l], g[o ^ 1][j][k][l]);
								} else if (!l) {
									upd(g[o][x][y][1], g[o ^ 1][j][k][l]);
								} else {
									upd(g[o][x][k ^ 1][l + (k == y ? -1 : 1)], g[o ^ 1][j][k][l]);
								}
							}
						}
					}
				}
			}
		}
	}
	if (s[1] != 'P') {
		upd(ans, f[n & 1][0][0][0]);
		upd(ans, f[n & 1][0][1][0]);
	}
	if (s[1] != 'Y') {
		upd(ans, g[n & 1][1][0][0]);
		upd(ans, g[n & 1][1][1][0]);
	}
	printf("%d\n", ans);
}

int main() {
	int T = 1;
	// scanf("%d", &T);
	while (T--) {
		solve();
	}
	return 0;
}