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#include <bits/stdc++.h>

using namespace std;
#define ll long long

struct tree {
    tree *l = nullptr, *r = nullptr;
    ll val = 0;
    ll i, j;
};

tree* nt(ll i, ll j, ll v) {
    tree* t = new tree;
    t->i = i;
    t->j = j;
    t->val = v;
    return t;
}

void add(tree* t, ll v) {


    // cout << v << " " << t->i << " " << t->j << " " << t->val << endl;

    if (v >= t->j || v < t->i) return;
    t->val++;

    if (t->j == v+1 && t->i == v) return;

    ll mid = (t->i + t->j) / 2;
    if (v < mid) {
        if (t->l == nullptr) t->l = nt(t->i, mid, 0);
        add(t->l, v);
    } else {
        if (t->r == nullptr) t->r = nt(mid, t->j, 0);
        add(t->r, v);
    }

}

ll cnt(tree* t, ll i, ll j) {

    if (i >= j) return 0;

    // cout << i << " " << j << endl;

    if (t->val == 0) return 0;

    if (j <= t->i || i >= t->j) return 0;
    i = max(i, t->i);
    j = min(j, t->j);
    
    if (j == t->j && i == t->i) return t->val;

    ll s = 0;
    if (t->l != nullptr) s += cnt(t->l, i, j);
    if (t->r != nullptr) s += cnt(t->r, i, j);

    return s;

}



int main() {

    ll n;
    cin >> n;

    vector<ll> a(n);
    for (auto &v : a) cin >> v;

    ll ma = 1LL << 35;
    tree* t = new tree;
    t->i = 0;
    t->j = ma;

    
    ll s = 0;
    for (int i = 0; i < n; i++) {
        // cout << a[i] << endl;
        s += cnt(t, a[i]+1, ma);
        // cout << cnt(t, a[i]+1, ma) << endl;
        // cout << "here" << endl;
        add(t, a[i]);
        // cout << "here" << endl;
    }

    cout << s << endl;

    return 0;

}

Test 1

Verdict: ACCEPTED

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Verdict: ACCEPTED

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Verdict: ACCEPTED

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Verdict: ACCEPTED

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Verdict: ACCEPTED

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Verdict: ACCEPTED

Test 71

Verdict: ACCEPTED