A7987 | Enemy is weak

The Romans have attacked again. This time they are much more than the Persians but Shapur is ready to defeat them. He says: "A lion is never afraid of a hundred sheep".

Nevertheless Shapur has to find weaknesses in the Roman army to defeat them. So he gives the army a weakness number.

In Shapur's opinion the weakness of an army is equal to the number of triplets $i,j,k$ such that $i<j<k$ and $a_{i}>a_{j}>a_{k}$ where $a_{x}$ is the power of man standing at position $x$ . The Roman army has one special trait — powers of all the people in it are distinct.

Help Shapur find out how weak the Romans are.
罗马人再次发动进攻。这次他们比波斯人强大得多，但沙普尔已经做好了打败他们的准备。他说："一头狮子永远不怕一百只绵羊"。

然而，沙普尔必须找到罗马军队的弱点才能打败他们。于是，他给军队编了一个弱点号码。

沙普尔认为，一支军队的弱点等于 i < j < k 和 ai > aj > ak 的三联数 i, j, k ，其中 ax 是站在 x 位置上的人的力量。罗马军队有一个特点--军队中所有人的力量都是不同的。

帮助沙普尔找出罗马人的弱点。

The first line of input contains a single number $n$ ( $3<=n<=10^{6}$ ) — the number of men in Roman army. Next line contains $n$ different positive integers $a_{i}$ ( $1<=i<=n,1<=a_{i}<=10^{9}$ ) — powers of men in the Roman army.
输入
第一行包含一个数字 $n$ ( $3<=n<=10^{6}$ ) - 罗马军队的人数。下一行包含 n 不同的正整数 $a_{i}$ ( $1<=i<=n,1<=a_{i}<=10^{9}$ ) - 罗马军队人数的幂

A single integer number, the weakness of the Roman army.

Please, do not use %lld specificator to read or write 64-bit integers in C++. It is preffered to use cout (also you may use %I64d).
输出
一个整数，即罗马军队的弱点。
请不要使用 %lld specificator 在 C++ 中读写 64 位整数。最好使用 cout(也可以使用 %I64d)。