#include<bits/stdc++.h>
#define pb push_back
#define x first
#define y second
#define pdd pair<double,double>
#define pii pair<int,int>
#define pll pair<LL,LL>
#define mp make_pair
#define LL long long
#define ULL unsigned long long
#define sqr(x) ((x)*(x))
#define pi acos(-1)
#define MEM(x) memset(x,0,sizeof(x))
#define MEMS(x) memset(x,-1,sizeof(x))
using namespace std;
const int mod=998244353;
const int P=998244353,root=3,MAXNUM=1<<23;
// Remember coefficient are mod P
/*
p=a*2^n+1 degree(poly) <= 2^n
n		2^n 				p 					a 		root
16  	65536 			    65537 				1 		3
20 	    1048576		 	    7340033 			7 		3
23                          998244353           119     3          
*/
int bigmod(long long a,int b){
	if(b==0)return 1;
	return (bigmod((a*a)%P,b/2)*(b%2?a:1ll))%P;
}
int inv(int a,int b){
	if(a==1)return 1;
	return (((long long)(a-inv(b%a,a))*b+1)/a)%b;
}
std::vector<long long> ps(MAXNUM);
std::vector<int> rev(MAXNUM);
    LL f_pow(unsigned int a,LL b){
        LL res=1,temp=a;
        while(b){
            if(b&1)res=res*temp%P;
            temp=temp*temp%P;
            b>>=1;
        }
        return res;
    }
struct poly{
	std::vector<unsigned int> co;
	int n;//polynomial degree = n
    poly(){n=0;co.clear();}
	poly(int d){n=d;co.resize(n+1,0);}
	void ntt(int NN){
		int r=0,st,N;
		unsigned int a,b;
		//while((1<<r)<(NN>>1))++r;//inv:r=0
		//for(N=2;N<=NN;N<<=1,--r){
        for(N=NN;N>1;N>>=1,r++){
			for(st=0;st<NN;st+=N){
				int i,ss=st+(N>>1);
				for(i=(N>>1)-1;i>=0;--i){
					a=co[st+i];// b=(ps[i<<r]*co[ss+i])%P;
                                b=co[ss+i];
					co[st+i]=a+b; if(co[st+i]>=P)co[st+i]-=P;
					///co[ss+i]=a+P-b; if(co[ss+i]>=P)co[ss+i]-=P;
                    co[ss+i]=((a+P-b)*ps[i<<r])%P;
				}
			}
		}
	}
	void ntt_inv(int NN){
    int r=0,st,N;
		unsigned int a,b;
		while((1<<r)<(NN>>1))++r;//inv:r=0
		for(N=2;N<=NN;N<<=1,--r){
        //inv for(N=NN;N>1;N>>=1,r++){
			for(st=0;st<NN;st+=N){
				int i,ss=st+(N>>1);
				for(i=(N>>1)-1;i>=0;--i){
					a=co[st+i]; b=(ps[i<<r]*co[ss+i])%P;
                                //inv b=co[ss+i];
					co[st+i]=a+b; if(co[st+i]>=P)co[st+i]-=P;
					co[ss+i]=a+P-b; if(co[ss+i]>=P)co[ss+i]-=P;
                    //inv co[ss+i]=((a+P-b)*ps[i<<r])%P;
				}
			}
		}
	}
    poly operator*(const poly& _b)const{
		poly a=*this,b=_b;
		int k=n+b.n,i,N=1;
		while(N<=k)N*=2;
		a.co.resize(N,0); b.co.resize(N,0);
		int r=bigmod(root,(P-1)/N),Ni=inv(N,P);
		ps[0]=1;
		for(i=1;i<N;++i)ps[i]=(ps[i-1]*r)%P;
		a.ntt(N);b.ntt(N);
		for(i=0;i<N;++i)a.co[i]=((long long)a.co[i]*b.co[i])%P;
		r=inv(r,P);
		for(i=1;i<N/2;++i)std::swap(ps[i],ps[N-i]);
		a.ntt_inv(N);
		for(i=0;i<N;++i)a.co[i]=((long long)a.co[i]*Ni)%P;
		a.n=n+_b.n; return a;
	}
};

char c[2000005];
vector<pair<poly,int> > dc(int l,int r){
    if(r-l<=1000){
        int dp[2][2][2005],dp2[2][2][2005];
        MEM(dp);
        MEM(dp2);
        if(c[l*2]!='Y')dp[0][0][1000]++;
        if(c[l*2]!='P')dp[1][1][1000]++;
        for(int i = l*2+2;i<=r*2;i+=2){
            if(c[i]!='Y'){
                for(int j = 0;j<2;j++){
                    for(int k = 0;k<2;k++){
                        if(k==0){
                            for(int a=0;a<=2000;a++){
                                if(c[i-1]=='?')
                                dp2[j][0][a]+=dp[j][k][a]*2%mod;
                                else dp2[j][0][a]+=dp[j][k][a];
                                dp2[j][0][a]%=mod;
                            }
                        }
                        else{
                            if(c[i-1]!='R')
                            for(int a=0;a<=2000;a++){
                                dp2[j][0][a]+=dp[j][k][a];
                                 dp2[j][0][a]%=mod;
                            }
                            if(c[i-1]!='B'){
                                for(int a=1;a<=2000;a++){
                                    dp2[j][0][a-1]+=dp[j][k][a];
                                    dp2[j][0][a-1]%=mod;
                                }
                            }
                        }
                    }
                }
            }
            if(c[i]!='P'){
                for(int j = 0;j<2;j++){
                    for(int k = 0;k<2;k++){
                        if(k==1){
                            for(int a=0;a<=2000;a++){
                                if(c[i-1]=='?')
                                dp2[j][1][a]+=dp[j][k][a]*2%mod;
                                else dp2[j][1][a]+=dp[j][k][a];
                                dp2[j][1][a]%=mod;
                            }
                        }
                        else{
                            if(c[i-1]!='R')
                            for(int a=0;a<=2000;a++){
                                dp2[j][1][a]+=dp[j][k][a];
                                dp2[j][1][a]%=mod;
                            }
                            if(c[i-1]!='B'){
                                for(int a=0;a<=1999;a++){
                                    dp2[j][1][a+1]+=dp[j][k][a];
                                    dp2[j][1][a+1]%=mod;
                                }
                            }
                        }
                    }
                }
            }
            for(int a=0;a<2;a++){
                for(int b=0;b<2;b++){
                    for(int c=0;c<=2000;c++){
                        dp[a][b][c]=dp2[a][b][c];
                        dp2[a][b][c]=0;
                       // if(dp[a][b][c])
                       // printf("%d %d %d %d %d\n",i,a,b,c-100,dp[a][b][c]);
                    }
                }
            }
        }
        vector<pair<poly,int> > v;
        for(int a=0;a<2;a++){
            for(int b=0;b<2;b++){
                int st=-1;
                poly p(0);
                p.co.clear();
                for(int c=0;c<=2000;c++){
                    if(dp[a][b][c]&&st==-1){
                        st=c;
                    }
                    if(st!=-1)p.co.push_back(dp[a][b][c]);
                }
                while(p.co.size()&&p.co.back()==0)p.co.pop_back();
                if(p.co.empty())p.co.pb(0),st=1000;
                p.n=p.co.size()-1;
                v.pb(mp(p,st-1000));
            }
        }
        return v;
    }
    else{
        int mid=(l+r)/2;
        auto v1=dc(l,mid);
        auto v2=dc(mid+1,r);
        vector<pair<poly,int> > v(4);

        for(int i = 0;i<4;i++){
            for(int j = 0;j<4;j++){
                int x1=i>>1,x2=i&1;
                int y1=j>>1,y2=j&1;
                poly p=v1[i].x*v2[j].x;
                LL a1=0,a2=0,a3=0;
                int d=v1[i].y+v2[j].y;
                int q=x1*2+y2;
                    reverse(v[q].x.co.begin(),v[q].x.co.end());
                    while(d<v[q].y){
                        v[q].y--;
                        v[q].x.co.pb(0);
                        v[q].x.n++;
                    }
                    reverse(v[q].x.co.begin(),v[q].x.co.end());
                LL a4=0;
                if(c[mid*2+1]!='R')
                for(int i = 0;i<p.co.size();i++){
                    while(v[q].x.co.size()<=i+d-v[q].y)v[q].x.co.pb(0),v[q].x.n++;
                    v[q].x.co[i+d-v[q].y]+=p.co[i];
                    v[q].x.co[i+d-v[q].y]%=mod;
                
                }
                if(c[mid*2+1]!='B'){
                    if(x2==0&&y1==1)d++;
                    if(x2==1&&y1==0)d--;
                    reverse(v[q].x.co.begin(),v[q].x.co.end());
                    while(d<v[q].y){
                        v[q].y--;
                        v[q].x.co.pb(0);
                        v[q].x.n++;
                    }
                    reverse(v[q].x.co.begin(),v[q].x.co.end());
                    for(int i = 0;i<p.co.size();i++){
                        while(v[q].x.co.size()<=i+d-v[q].y)v[q].x.co.pb(0),v[q].x.n++;
                        v[q].x.co[i+d-v[q].y]+=p.co[i];
                        v[q].x.co[i+d-v[q].y]%=mod;
                    }
                }
               // printf("%d %d\n",v[q].x.n,p.n);
            }
        }
       /* printf("ans: %d %d\n ",l,r);
        for(int i = 0;i<4;i++){
            printf("%d\n",v[i].y);
            for(auto it:v[i].x.co)printf("%d ",it);
            printf("\n");
        }*/
        return v;
    }
}
void solve(int T){
    int n;
    scanf("%d",&n);
    scanf("%s",c);
   // for(int i = 0;i<2*n;i++)c[i]='?';
    auto p=dc(0,n-1);
    LL ans=0;
    for(int i = 0;i<2;i++){
        for(int j = 0;j<2;j++){
            int q=i*2+j;
            if(i==j){
                if(c[2*n-1]!='R'){
                    int need=-p[q].y;
                    if(p[q].x.co.size()>need&&need>=0)ans+=p[q].x.co[need];
                }
                if(c[2*n-1]!='B'){
                    int need=-p[q].y;
                    if(p[q].x.co.size()>need&&need>=0)ans+=p[q].x.co[need];
                }
            }
            else{
                if(c[2*n-1]!='R'){
                    int need=-p[q].y;
                    if(p[q].x.co.size()>need&&need>=0)ans+=p[q].x.co[need];
                }
                if(c[2*n-1]!='B'){
                    int need=-p[q].y;
                    if(j==0&&i==1)need--;
                    if(j==1&&i==0)need++;
                      if(p[q].x.co.size()>need&&need>=0)ans+=p[q].x.co[need];
                }
            }
        }
    }
    printf("%lld\n",ans%mod);
}
int main(){
   
    int t=1;0000;
    for(int i = 1;i<=t;i++){
        solve(i);
    }
    return 0;
}
/*
1543904 3707852 107840
1 23
JAY'S SON JA$ON


3 4
1 2 1 3
1 3 1 5
1 2 2 2
1 3 3 5
*/