/* Author: Nguyen Chi Thanh - High School for the Gifted - VNU.HCM (i2528) */ #include <bits/stdc++.h> using namespace std; #define int long long #define ull unsigned long long #define ld long double #define pii pair<int, int> #define fi first #define se second #define __builtin_popcount __builtin_popcountll #define all(x) (x).begin(), (x).end() #define BIT(x, i) (((x) >> (i)) & 1) #define MASK(x) ((1ll << (x))) #define debug(a, l, r) for (int _i = (l); _i <= (r); ++_i) cout << (a)[_i] << ' '; cout << '\n'; struct FenwickTree { int n; vector<int> fen; FenwickTree(int _n) : n(_n), fen(n + 5, 0) {} void update(int idx, int v) { for (int i = idx; i <= n; i += i & -i) fen[i] += v; } int get(int idx) { int sum = 0; for (int i = idx; i; i -= i & -i) sum += fen[i]; return sum; } }; const int MAXN = 3e5 + 5; int n, a[MAXN]; void init() { cin >> n; vector<int> vals; for (int i = 1; i <= n; ++i) { cin >> a[i]; vals.push_back(a[i]); } sort(all(vals)); vals.erase(unique(all(vals)), end(vals)); for (int i = 1; i <= n; ++i) a[i] = (int)(lower_bound(all(vals), a[i]) - begin(vals)) + 1; } void solve() { FenwickTree fen_left(n + 5), fen_right(n + 5); fen_left.update(a[1], 1); for (int i = 3; i <= n; ++i) fen_right.update(a[i], 1); int res = 0; for (int i = 2; i < n; ++i) { int mul_left = fen_left.get(a[i] - 1); int mul_right = fen_right.get(a[i] - 1); int contrib = mul_left * mul_right; res += contrib; fen_left.update(a[i], 1); fen_right.update(a[i + 1], -1); } cout << res; } signed main() { #ifdef NCTHANH freopen("input.txt", "r", stdin); freopen("output.txt", "w", stdout); #endif ios_base::sync_with_stdio(0); cin.tie(nullptr); cout.tie(nullptr); init(); solve(); return 0; }