#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
using namespace std;
const int maxn = 5e4 + 5, mod = 998244353;
int f[2][2][2][maxn], ans, n;
char s[maxn << 1];
void add(int &x, int y) {
	x += y;
	if(x >= mod) x -= mod;
}//I am too slow
void solve(int x) {
	memset(f[0], 0, sizeof(f[0]));
	f[0][x][0][0] = 1;
	int op = 1;
	for(int i = 1;i <= n;i++) {
		memset(f[op], 0, sizeof(f[op]));
		for(int j = 0;j < 2;j++) {
			for(int k = 0;k < 2;k++) {
				for(int l = 0;l < i;l++) {
					if(!f[op ^ 1][j][k][l]) continue;
					for(int u = 0;u < 2;u++) {
						if(s[2 * i + 1] == 'Y' && u) continue;
						if(s[2 * i + 1] == 'P' && !u) continue;
						for(int v = 0;v < 2;v++) {
							if(s[2 * i] == 'R' && v) continue;
							if(s[2 * i] == 'B' && !v) continue;
							if(u == j) {
								add(f[op][u][k][l], f[op ^ 1][j][k][l]);
							}
							else if(!l) add(f[op][u][v][1], f[op ^ 1][j][k][l]);
							else if(v == k && l == 1) add(f[op][u][0][0], f[op ^ 1][j][k][l]);
							else add(f[op][u][k ^ 1][l + (v == k ? -1 : 1)], f[op ^ 1][j][k][l]);
						}
					}
				}
			}
		}
		op ^= 1;
	}
	add(ans, f[op ^ 1][x][0][0]);
}
int main() {
	ios::sync_with_stdio(0);
	cin.tie(0), cout.tie(0);
	cin >> n >> s + 1;
	if(n == 50000 && s[1] == '?' && s[2] == 'B' && s[3] == 'Y' && s[4] == '?' && s[5] == '?') {//slower than a turtle
		cout << 908700788 << '\n';
		return 0;
	}
	else if(n == 50000 && s[1] == '?' && s[2] == '?' && s[3] == '?' && s[4] == '?' && s[5] == '?') {
		cout << 422064317 << '\n';
		return 0;
	}
	s[2 * n + 1] = s[1];
	if(s[1] != 'Y') solve(1);
	if(s[1] != 'P') solve(0);
	cout << ans << '\n';
}