#include<iostream>
#include<cstring>
#include<cstdio>
#include<algorithm>
using namespace std;
const int Mod=998244353;
int n,K;
#define Maxn 305
char S[Maxn];
int a[Maxn],cnt=0;
int dp[Maxn][Maxn][Maxn];
int main(){
	scanf("%s",S+1);scanf("%d",&K);
	n=strlen(S+1);
	S[n+1]='0';
	n++;
	int lst=0;
	for(int i=1;i<=n;++i)
	    if(S[i]=='0'){
	    	a[++cnt]=i-lst-1;
	    	lst=i;
		}
	reverse(a+1,a+cnt+1);
	int sum=0;
	dp[0][0][0]=1;
	for(int i=0;i<cnt;++i){
		for(int j=0;j<=sum;++j)
		    for(int k=0;k<=j;++k){
		    	dp[i+1][j][k]=dp[i][j][k];
		    	if(k){
		    		dp[i+1][j][k]+=dp[i+1][j][k-1];
		    		if(dp[i+1][j][k]>=Mod)dp[i+1][j][k]-=Mod;
				}
			}
		for(int j=0;j<=sum;++j)
		    for(int k=0;k<=j;++k)
		        for(int l=1;l<=a[i+1];++l){
		        	dp[i+1][j+l][k]+=dp[i][j][k];
		        	if(dp[i+1][j+l][k]>=Mod)dp[i+1][j+l][k]-=Mod;
				}
		sum+=a[i+1];
	}
	int Ans=0;
	for(int i=0;i<=min(K,sum);++i){
		Ans+=dp[cnt][i][i];
		if(Ans>=Mod)Ans-=Mod;
	}
	printf("%d\n",Ans);
	return 0;
}
#include <bits/stdc++.h>
using namespace std;

#define int long long
#define rep(i,l,r) for(int i=(int)(l);i<(int)(r);i++)
#define all(x) (x).begin(),(x).end()
#define sz(x) ((int)x.size())
template<class T>bool chmax(T &a,T b){if(a<b){a=b;return 1;}return 0;}
template<class T>bool chmin(T &a,T b){if(a>b){a=b;return 1;}return 0;}

typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<vi> vvi;

const int inf = 1LL<<60;
const int mod = 1e9 + 7;
const double eps = 1e-9;

/*{
  }*/

signed main(){
  int n;
  string s;
  cin >> n >> s;

  vi a(2*n);
  rep(i, 0, 2*n){
    a[i] = ((s[i] == 'B') + (i%2 == 0)) % 2;
  }

  int ans = 1, cnt = 0;
  rep(i, 0, 2*n){
    if(a[i]){
      (ans *= cnt) %= mod;
      cnt--;
    }else{
      cnt++;
    }
  }

  if(cnt) ans = 0;

  rep(i, 1, n+1) (ans *= i) %= mod;

  cout << ans << endl;
  
//  rep(i, 0, 2*n) cout << a[i] << " ";
//  cout << endl;

  return 0;
}
