Problem:
Score : 300 points

Problem Statement

Given is an integer sequence D_1,...,D_N of N elements. Find the number, modulo 998244353, of trees with N vertices numbered 1 to N that satisfy the following condition:

For every integer i from 1 to N, the distance between Vertex 1 and Vertex i is D_i.

Notes

A tree of N vertices is a connected undirected graph with N vertices and N-1 edges, and the distance between two vertices are the number of edges in the shortest path between them.

Two trees are considered different if and only if there are two vertices x and y such that there is an edge between x and y in one of those trees and not in the other.

Constraints

1 \leq N \leq 10^5

0 \leq D_i \leq N-1

Input

Input is given from Standard Input in the following format:

N
D_1 D_2 ... D_N

Output

Print the answer.

Sample Input 1

4
0 1 1 2

Sample Output 1

2

For example, a tree with edges (1,2), (1,3), and (2,4) satisfies the condition.

Sample Input 2

4
1 1 1 1

Sample Output 2

0

Sample Input 3

7
0 3 2 1 2 2 1

Sample Output 3

24

Solution in Python (3.4.3) (judge verdict: Runtime Error)

n = int(input()) 
l = list(map(int, input().split()))
if l[0] != 0:
    print(0)
    exit()

max_vertex = max(l)
ll = []
l=sorted(l)
l.append('end')
c=1
for i in range(1, n):
    if l[i] != l[i+1]:
        if c == 0:
            print(0)
            exit();
        ll.append(c)
        c = 0
    c+=1
   
count = 1
for i in range(1, max_vertex):
    tmp = ll[i-1]
    count *= pow(tmp, ll[i])
print(count%998244353)