Dobri

    1#include <bits/stdc++.h>
    2using namespace std;
    3using ll = long long;
    4using i128 = __int128;
    5const int inf = 1e9;
    6const ll INF = 1e18; //❄️
    7int main() {
    8    ios::sync_with_stdio(0); cin.tie(0); 
    9    int n; cin >> n;
    10    vector<int> v(n);
    11    unordered_map<int, int> f;
    12    for (int i = 0; i < n; i++) {
    13        cin >> v[i];
    14    }
    15    for (int i = 0; i < n; i++) {
    16        for (int j = 0; j <= i; j++) {
    17            if (!f.count(v[i] + v[j])) f[v[i] + v[j]] = i;
    18        }
    19    }
    20    int cnt = 0;
    21    for (int i = 0; i < n; i++) {
    22        for (int j = 0; j < i; j++) {
    23            int cur = v[i] - v[j];
    24            if (f.count(cur) && f[cur] < i) {
    25                cnt++;
    26                break;
    27            }
    28        }
    29    }
    30    cout << cnt << '\n';
    31    return 0;
    32}