## https://yukicoder.me/problems/no/2898

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():
    N = int(input())
    A = list(map(int, input().split()))

    # 下準備
    free = 0
    used = 0
    for i in range(N):
        if A[i] == -1:
            free += 1
        else:
            used += 1
    
    # 下準備2
    a_array = [a for a in A if a != -1]
    a_array.sort()
    a_map = {}
    for i in range(len(a_array)):
        a_map[a_array[i]] = i + 1

    answer = 0
    combi = CombinationCalculator(N, MOD)
    fixed_max_a = -1
    before_used = 0
    for m in range(N):
        if A[m] == -1:
            free -= 1
            ans = combi.calc_permutation(N - used, m + 1 - before_used)
            if fixed_max_a != -1:
                ans -= combi.calc_permutation(fixed_max_a - a_map[fixed_max_a], m + 1 - before_used)
                ans %= MOD
            
            ans *= pow(m + 1 - before_used, MOD - 2, MOD)
            ans %= MOD

            # 残り部分の組み合わせ
            ans *= combi.factorial[free]
            ans %= MOD
        else:
            before_used += 1
            if fixed_max_a > A[m]:
                continue

            ans = combi.calc_permutation(A[m] - a_map[A[m]], m + 1 - before_used)

            # 残り部分の組み合わせ
            ans *= combi.factorial[free]
            ans %= MOD
            fixed_max_a = max(fixed_max_a, A[m])
        answer += ans
        answer %= MOD
    print(answer)
            







    





                





    
        















if __name__ == "__main__":
    main()