#include <bits/stdc++.h> using namespace std; #define int long long struct FenwickTree { vector<int> bit; int n; FenwickTree(int n) { this -> n = n; bit.assign(n + 1, 0); } int query(int k) { int res = 0; for (; k >= 1; k -= k & -k) { res += bit[k]; } return res; } int query(int l, int r) { return query(r) - query(l - 1); } void update(int k, int d) { for (; k <= n; k += k & -k) { bit[k] += d; } } }; signed 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]; } auto b = h; sort(b.begin(), b.end()); for (int i = 0; i < n; i++) { h[i] = lower_bound(b.begin(), b.end(), h[i]) - b.begin() + 1; } FenwickTree left(n + 5), right(n + 5); for (int i = 0; i < n; i++) { right.update(h[i], 1); } int res = 0; for (int i = 0; i < n; i++) { res += left.query(h[i] - 1) * right.query(h[i] - 1); left.update(h[i], 1); right.update(h[i], -1); } cout << res << '\n'; return 0; }