#include <bits/stdc++.h>
using namespace std;
#define int long long
int n,a[200000],ans,mod = 1000000007ll,cnt[7000],mx;

signed main(){
	cin >> n;
	for(int i = 1; i <= n; i++){
		cin >> a[i];
		mx = max(mx,a[i]);
		cnt[a[i]]++;
	}
	for(int i = 2; i <= mx; i++){
		if(cnt[i] < 2) continue;
		int x = (cnt[i] - 1) * cnt[i] / 2 % mod;
		for(int j = 1; j <= i / 2; j++){
			if(j == i - j){
				if(cnt[j] > 1)
				ans += x * cnt[j] * (cnt[j] - 1) / 2 % mod;
			}else{
				if(cnt[j] > 0 && cnt[i - j] > 0)
				ans += x * cnt[j] * cnt[i - j] % mod;
			}
		}
	}
	cout << ans;
	return 0;
}

前三个测试点AC,其他WA，不调完不睡觉