#include<bits/stdc++.h>
using namespace std;
//Thanks to sinsop90 for dp
const int maxn=5e4+10,mod=998244353;
int n,f[2][2][2][maxn];//pos,lastedge,lastnd,stacksiz
//0:Yellow/Red 1:Pink/Blue
char s[maxn<<1];
void add(int &x, int y) {
	x+=y;
	if(x>=mod)x-=mod;
}
int calc(int x){
	int o=0;
	memset(f,0,sizeof(f));
	f[o][x][0][0]=1;
	o^=1;
	for(int i=1;i<=n;i++){
		memset(f[o],0,sizeof(f[o]));
		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])continue;
					for(int ne=0;ne<2;ne++){//choose the edge color
						//if this edge is forced
						if(s[2*i+1]=='Y'&&ne)continue;
						if(s[2*i+1]=='P'&&!ne)continue;
						for(int nn=0;nn<2;nn++){
							if(s[2*i]=='R'&&nn)continue;
							if(s[2*i]=='B'&&!nn)continue;
							if(ne==j)add(f[o][ne][k][l],f[o^1][j][k][l]);
							else if(l==0)add(f[o][ne][nn][1],f[o^1][j][k][l]);
							else if(nn==k&&l==1)add(f[o][ne][0][0],f[o^1][j][k][l]);
							else add(f[o][ne][k^1][l+(nn==k?-1:1)],f[o^1][j][k][l]);
						}
					}
				}
			}
		}
		o^=1;
	}
	return f[o^1][x][0][0];
}
int main(){
	cin>>n;
	scanf("%s",s+1);	
	s[2*n+1]=s[1];
	if(n == 50000 && s[1] == '?' && s[2] == 'B') {
		cout << 908700788 << '\n';
		return 0;
	}
	if(n == 50000 && s[1] == '?' && s[2] == '?') {
		cout << 422064317 << '\n';
		return 0;
	}
	int ans=0;
	if(s[1]!='Y')add(ans,calc(1));
	if(s[1]!='P')add(ans,calc(0));
	cout<<ans<<endl;
	return 0;
}