#define MD 998244353
ll@N,@K,@A[N],@B[N];Mint a=0,t[N+1]{1},s,p;REP(m,K-1,K+1){s=p=1;rep(i,N)s=(i<m?s:s-p*t[i-m])*A[i]+(t[i+1]=s*B[i]),p*=A[i],i<m?p:p/=A[i-m];s=0;p=1;REP(k,m+1)s+=t[N-k]*p,p*=A[N-1-k];a+=m<K?-s:s;}wt(a);