这是代码，dalao帮忙看看

#include<bits/stdc++.h>

using namespace std;
const int mod = 998244353998244353;

int n;
int a[1005];
int f[4005][40005];
int ans;


int main(){
	scanf("%d" , &n);
	for(int i = 1 ; i <= n ; i++){
		scanf("%d" , &a[i]);
	}	
	
	for(int i = 1 ; i <= n ; i++){
		ans++;
		for(int j = i - 1 ; j > 0 ; j--){
			int d = a[i] - a[j] + 20010;
			f[i][d] = (f[i][d] + f[j][d] + 1) % mod;
			ans = (ans + f[j][d] + 1) % mod; 
			
		}
	}
	
	printf("%d" , ans);
	return 0;
}