#define MD 998244353
ll@N,A[2N]{};A[0..N-1]=rd_ll();Comb<Mint>c;wt(sum[i,0,2N](sum[j,A[i],i?max(A[i]+1,A[i-1]):*A+1]((i&&A[i-1]>j)*c.C(j+i-1,j)+(i<N&&A[i]==j)*c.C(j-1+i,i))));