都只A了一点点

import java.util.*;
import java.io.*;

public class Main1 {
    public static void main(String[] args) {
        Scanner cin = new Scanner(System.in);

        while (cin.hasNext()) {
            int n = cin.nextInt();
            int[] aNums = new int[n-1];
            for (int i = 0; i < n-1; ++i) {
                aNums[i] = cin.nextInt();
            }

            int[] sum = new int[1];
            sum[0] = 0;
            List<Integer> tmp = new LinkedList<>();
            genNums(n, tmp, sum, aNums);
            System.out.println(sum[0]);
        }
    }

    public static void genNums(int n, List<Integer> tmp, int[] sum, int[] aNums) {
        if (tmp.size() == n) {
            sum[0] = sum[0] + 1;
        } else {
            for (int i = 1; i < n+1; ++i) {
                if (!tmp.contains(i)) {
                    if (check(tmp, i-1, aNums)) {
                        tmp.add(i);
                        genNums(n, tmp, sum, aNums);
                        tmp.remove(tmp.size()-1);
                    }
                }
            }
        }
    }

    public static boolean check(List<Integer> tmp, int i, int[] aNums) {
        if (tmp.isEmpty()) return true;

        int pre = tmp.get(tmp.size()-1);
        int index = tmp.size() - 1;
        if (aNums[index] == 0) {
            if (pre < i + 1) {
                return true;
            }
        } else {
            if (pre > i + 1) {
                return true;
            }
        }

        return false;
    }
}

# ac 27%
def solver(n, m):
    def genNums(n, m, cur):
        nonlocal tmp, total, dem, retA
        if m == 0 and n == 0:
            dem += 1
            if check(tmp):
                retA += 1
        else:
            for i in range(cur, total):
                p = ['A', 'B', 'C'][cur % 3]
                if n > 0:
                    tmp.append(p+'0')
                    genNums(n-1, m, i+1)
                    tmp.pop()
                if m > 0:
                    tmp.append(p+'1')
                    genNums(n, m-1, i + 1)
                    tmp.pop()
    tmp = []
    total = m + n
    dem = 0
    retA  = 0
    genNums(n, m, 0)

    ret = float('%.5f' % (retA / dem))


    return ret

def check(tmp):
    retA = 0
    for n in tmp:
        # print(n)
        if n[1] == '0' and n[0] == 'A':
            retA += 1
            break
        elif n[1] == '0' and n[0] == 'B':
            break

    return retA