MOD=998244353
class Combination:
    def __init__(self, n:int, mod:int=10**9+7):
        self._n = n
        self._mod = mod
        self.fac  = [1]*(n+1)
        fac=1
        for i in range(2, n+1): self.fac[i] = fac = fac * i % mod
        ifac=pow(fac, mod-2, mod)
        self.ifac = [1]*n
        self.ifac.append(ifac)
        for i in range(n,0,-1): self.ifac[i-1] = ifac = ifac * i % mod
    def fact(self, n:int) -> int:
        return self.fac[n]
    def nCr(self, n:int, r:int) -> int:
        if r<0 or r>n or n<0:return 0
        return self.fac[n] * self.ifac[r] % self._mod * self.ifac[n-r] % self._mod

X,Y,Z,W=map(int,input().split())

if Z==0:
    Z=1
else:
    W=1

cmb = Combination(max(X,Y)*2, MOD)

ans = cmb.nCr(X-Z+Y-W, Y-W)

for i in range(X, Z, -1):
    ans *= i
    ans %= MOD
for i in range(Y, W, -1):
    ans *= i
    ans %= MOD
print(ans)