vector.cpp

#include<iostream>
#include<cstdlib>
#include<vector>
#include<unordered_map>
#include<algorithm>

#define long long long
#define nln '\n'

const long N = 30, BASE = 1e4;

using namespace std;

pair<long, long> operator + (pair<long, long> a, pair<long, long> b)
{
    return {a.first+b.first, a.second+b.second};
}

pair<long, long> operator - (pair<long, long> a, pair<long, long> b)
{
    return {a.first-b.first, a.second-b.second};
}

void sums(
    const vector<pair<long, long>> &a,
    const pair<long, long> &mdl,
    long bgn, long end,
    const pair<long, long> &psm,
    vector<pair<long, long>> &vsm,
    unordered_map<long, long> &cnt
    )
{
    if (bgn == end)
    {
        if (!cnt[psm.first*BASE+psm.second])
            vsm.push_back(psm), cnt[psm.first*BASE+psm.second] = 1;
        else
            ++cnt[psm.first*BASE+psm.second];
        return;
    }
    sums(a, mdl, bgn+1, end, psm+a[bgn], vsm, cnt);
    sums(a, mdl, bgn+1, end, psm, vsm, cnt);
}

int main()
{
    cin.tie(0)->sync_with_stdio(0);
    cout.tie(0)->sync_with_stdio(0);
    // Input
    //freopen("vector.inp", "r", stdin);
    long n;
    cin >> n;
    vector<pair<long, long>> a(n);
    for (auto &i : a)
        cin >> i.first >> i.second;
    long u, v;
    cin >> u >> v;
    // Process
    vector<pair<long, long>> sm1, sm2;
    unordered_map<long, long> co1, co2;

    sums(a, {u, v}, 0, n/2, {0, 0}, sm1, co1);
    sums(a, {u, v}, n/2, n, {0, 0}, sm2, co2);

    sort(sm2.begin(), sm2.end());

    long ans = 0;
    for (const auto &i : sm1)
    {
        pair<long, long> tem = make_pair(u, v)-i;
        if (binary_search(sm2.begin(), sm2. end(), tem))
            ans += co1[i.first*BASE+i.second]*co2[tem.first*BASE+tem.second];
    }

    cout << ans << nln;
    return 0;
}