#include <bits/stdc++.h> using namespace std; typedef long long ll; struct Fenwick { int n; vector<ll> bit; Fenwick(int n) : n(n), bit(n + 1, 0) {} void update(int idx, ll val) { for (++idx; idx <= n; idx += idx & -idx) bit[idx] += val; } ll query(int idx) { ll sum = 0; for (++idx; idx > 0; idx -= idx & -idx) sum += bit[idx]; return sum; } }; int main() { ios::sync_with_stdio(false); cin.tie(nullptr); int n; cin >> n; vector<int> H(n); for (int i = 0; i < n; i++) cin >> H[i]; // Coordinate compression vector<int> sorted = H; sort(sorted.begin(), sorted.end()); sorted.erase(unique(sorted.begin(), sorted.end()), sorted.end()); for (int i = 0; i < n; i++) { H[i] = lower_bound(sorted.begin(), sorted.end(), H[i]) - sorted.begin(); } Fenwick fenwLeft(sorted.size()); vector<ll> leftSmaller(n); // Count smaller on left for (int i = 0; i < n; i++) { leftSmaller[i] = fenwLeft.query(H[i] - 1); fenwLeft.update(H[i], 1); } Fenwick fenwRight(sorted.size()); vector<ll> rightSmaller(n); // Count smaller on right for (int i = n - 1; i >= 0; i--) { rightSmaller[i] = fenwRight.query(H[i] - 1); fenwRight.update(H[i], 1); } ll ans = 0; for (int i = 0; i < n; i++) { ans += leftSmaller[i] * rightSmaller[i]; } cout << ans << "\n"; }