import sys
import numpy as np
input = sys.stdin.readline
def read_values(): return map(int, input().split())
def read_index(): return map(lambda x: int(x) - 1, input().split())
def read_list(): return list(read_values())
def read_lists(N): return [read_list() for _ in range(N)]

def main():
    n=int(input())
    a=read_list()
    na=np.array(a, dtype=object)
    a.reverse()
    ans=1
    ans2=1
    for i in range(len(a)):
        na=na[:-1]
        mul1=np.prod(na-a[i])%998244353
        ans*=mul1
        ans%=998244353
        	
    print(ans)   

if __name__ == "__main__":
    main()