import sys
readline=sys.stdin.readline

def Extended_Euclid(n,m):
    stack=[]
    while m:
        stack.append((n,m))
        n,m=m,n%m
    if n>=0:
        x,y=1,0
    else:
        x,y=-1,0
    for i in range(len(stack)-1,-1,-1):
        n,m=stack[i]
        x,y=y,x-(n//m)*y
    return x,y

class MOD:
    def __init__(self,p,e=None):
        self.p=p
        self.e=e
        if self.e==None:
            self.mod=self.p
        else:
            self.mod=self.p**self.e

    def Pow(self,a,n):
        a%=self.mod
        if n>=0:
            return pow(a,n,self.mod)
        else:
            #assert math.gcd(a,self.mod)==1
            x=Extended_Euclid(a,self.mod)[0]
            return pow(x,-n,self.mod)

    def Build_Fact(self,N):
        assert N>=0
        self.factorial=[1]
        if self.e==None:
            for i in range(1,N+1):
                self.factorial.append(self.factorial[-1]*i%self.mod)
        else:
            self.cnt=[0]*(N+1)
            for i in range(1,N+1):
                self.cnt[i]=self.cnt[i-1]
                ii=i
                while ii%self.p==0:
                    ii//=self.p
                    self.cnt[i]+=1
                self.factorial.append(self.factorial[-1]*ii%self.mod)
        self.factorial_inve=[None]*(N+1)
        self.factorial_inve[-1]=self.Pow(self.factorial[-1],-1)
        for i in range(N-1,-1,-1):
            ii=i+1
            while ii%self.p==0:
                ii//=self.p
            self.factorial_inve[i]=(self.factorial_inve[i+1]*ii)%self.mod

    def Build_Inverse(self,N):
        self.inverse=[None]*(N+1)
        assert self.p>N
        self.inverse[1]=1
        for n in range(2,N+1):
            if n%self.p==0:
                continue
            a,b=divmod(self.mod,n)
            self.inverse[n]=(-a*self.inverse[b])%self.mod
    
    def Inverse(self,n):
        return self.inverse[n]

    def Fact(self,N):
        if N<0:
            return 0
        retu=self.factorial[N]
        if self.e!=None and self.cnt[N]:
            retu*=pow(self.p,self.cnt[N],self.mod)%self.mod
            retu%=self.mod
        return retu

    def Fact_Inve(self,N):
        if self.e!=None and self.cnt[N]:
            return None
        return self.factorial_inve[N]

    def Comb(self,N,K,divisible_count=False):
        if K<0 or K>N:
            return 0
        retu=self.factorial[N]*self.factorial_inve[K]%self.mod*self.factorial_inve[N-K]%self.mod
        if self.e!=None:
            cnt=self.cnt[N]-self.cnt[N-K]-self.cnt[K]
            if divisible_count:
                return retu,cnt
            else:
                retu*=pow(self.p,cnt,self.mod)
                retu%=self.mod
        return retu

def Hook_Length_Formula(lst,mod=0):
    lst=sorted(lst)
    le=[0]*lst[-1]
    nume,deno=1,1
    s=0
    for l in lst:
        for j in range(l):
            nume*=s+1
            deno*=le[j]+l-j
            s+=1
            le[j]+=1
            if mod:
                nume%=mod
                deno%=mod
    if mod:
        retu=nume*MOD(mod).Pow(deno,-1)%mod
    else:
        retu=nume//deno
    return retu

N=int(readline())
A=[0]+list(map(int,readline().split()))
mod=998244353
if sum(A)%2:
    ans=0
else:
    MD=MOD(mod)
    MD.Build_Fact(N*max(A))
    lst=[]
    for i in range(N):
        for _ in range(A[i+1]-A[i]):
            lst.append(1)
        lst.append(0)
    lst0=lst[::2]
    lst1=lst[1::2]
    L,R=[0],[]
    for i in range(len(lst0)):
        if lst0[i]==0:
            L.append(i+1)
            R.append(i)
    R.append(len(lst0))
    lst0=[r-l for l,r in zip(L,R)]
    for i in range(1,len(lst0)):
        lst0[i]+=lst0[i-1]
    L,R=[0],[]
    for i in range(len(lst1)):
        if lst1[i]==0:
            L.append(i+1)
            R.append(i)
    R.append(len(lst1))
    lst1=[r-l for l,r in zip(L,R)]
    for i in range(1,len(lst1)):
        lst1[i]+=lst1[i-1]
    ans=Hook_Length_Formula(lst0[:-1][::-1],mod)*Hook_Length_Formula(lst1[:-1][::-1],mod)%mod
    ans*=MD.Comb(sum(lst0[:-1])+sum(lst1[:-1]),sum(lst0[:-1]))
    ans%=mod
print(ans)