$\Omicron\left(n^2\right)$暴力可过

#include <bits/stdc++.h>
using namespace std;
char *p1, *p2, buf[100000];
#define nc() (p1==p2 && (p2=(p1=buf)+fread(buf,1,100000,stdin),p1==p2)?EOF:*p1++)
inline int rd() 
{
	int x = 0, f = 1; char c = nc();
	while (c < 48 || c > 57) f = (c == '-') ? -1 : 1, c = nc();
	while (c >= 48 && c <= 57)	x = x*10 + c-48, c = nc();
	return x*f;
}

#define int long long
int n, a[30005], res;

signed main() 
{
//	freopen("P1637.txt", "r", stdin);
	n = rd();
	for (int i = 1; i <= n; ++i) a[i] = rd();
	for (int k = 1; k <= n; ++k) {
		int l = 0, r = 0;
		for (int i = 1; i <= k - 1; ++i) if (a[i] < a[k]) ++l;
		for (int j = k + 1; j <= n; ++j) if (a[j] > a[k]) ++r;
		res += l * r;
	}
	printf("%lld\n", res);
	return 0;
}