# https://yukicoder.me/problems/no/895

MOD = 998244353


class CombinationCalculator:
    """
    modを考慮したPermutation, Combinationを計算するためのクラス
    """    
    def __init__(self, size, mod):
        self.mod = mod
        self.factorial = [0] * (size + 1)
        self.factorial[0] = 1
        for i in range(1, size + 1):
            self.factorial[i] = (i * self.factorial[i - 1]) % self.mod
        
        self.inv_factorial = [0] * (size + 1)
        self.inv_factorial[size] = pow(self.factorial[size], self.mod - 2, self.mod)

        for i in reversed(range(size)):
            self.inv_factorial[i] = ((i + 1) * self.inv_factorial[i + 1]) % self.mod

    def calc_combination(self, n, r):
        if n < 0 or n < r or r < 0:
            return 0

        if r == 0 or n == r:
            return 1
        
        ans = self.inv_factorial[n - r] * self.inv_factorial[r]
        ans %= self.mod
        ans *= self.factorial[n]
        ans %= self.mod
        return ans
    
    def calc_permutation(self, n, r):
        if n < 0 or n < r:
            return 0

        ans = self.inv_factorial[n - r]
        ans *= self.factorial[n]
        ans %= self.mod
        return ans
        

def main():
    x, y = map(int, input().split())

    if not (x <= 4000 and y <= 4000):
        return

    combi = CombinationCalculator(x + y, MOD)
    answer = 0

    pow2 = [0] * (x + y + 1)
    p = 1
    for k in range(x + y + 1):
        pow2[k] = p
        p *= 2
        p %= MOD

    for z1 in range(min(x, y) + 1):
        for z0 in range(z1 + 1):

            ans = combi.factorial[x + y - 2 * z1 + z0]
            ans *= combi.inv_factorial[x - z1]
            ans %= MOD
            ans *= combi.inv_factorial[y - z1]
            ans %= MOD
            ans *= combi.inv_factorial[z0]
            ans %= MOD
            ans *= pow2[z0]
            ans %= MOD
            answer += ans
            answer %= MOD
    print(answer)




if __name__ == "__main__":
    main()