#int(input())
#map(int, input().split())
#list(map(int, input().split()))

X, Y, Z, W = map(int, input().split())
mod = 998244353

if Z == 0:
    X, Y = Y, X
    Z, W = W, Z

m = 6 * 10 ** 5 + 10

fac = [1] * (m + 1)
facinv = [1] * (m + 1)
for i in range(1, m+1):
    fac[i] = (fac[i-1] * i) % mod
    facinv[i] = (facinv[i-1] * pow(i, mod-2, mod)) % mod

def nCk(n, k):
    return (fac[n] * facinv[k] * facinv[n-k]) % mod

u = X - Z
v = Y - W

ans = nCk((u+v-1), u)
# print(u, v, ans)
ans = (ans * fac[X] * facinv[Z]) % mod
ans = (ans * fac[Y]) % mod


print(ans)