#include <iostream>
#include <bits/stdc++.h>
using namespace std;
#define int long long
int a[6000];
bool used[2000000];
    vector <int> q;
 main()
{
    set<int> s;
    int n, kol = 0, kol2 = 1e6;
    cin >> n;
    for(int i =0 ; i < n; i++){
            cin >> a[i];
            if(a[i] < 0){
                if(used[abs(a[i]) + kol2]) kol++;
            }
            else{
                if(used[a[i]]) kol ++;
            }
            if(s.find(a[i]) == s.end()){
                q.push_back(a[i]);
            for(int j = 0; j < q.size(); j++){
                for(int o = 0; o < q.size(); o++){
                    int h = a[i] + q[j] + q[o];
                    if(h >= 0 )used[h] = 1;
                    else used[abs(h)+ kol2] =1;
                }
            }
                s.insert(a[i]);
            }
    }
    cout << kol;

}