跳到主要内容
图灵 OJTURING / ONLINE JUDGE

#F1403. Enemy is weak

    ID: 1409 传统题 2000ms 256MiB 尝试: 0 已通过: 0 难度: 6 上传者: 标签>数据结构提高难度共享题库Codeforces英文题面题目来源题面语言

Enemy is weak

题目描述

E. Enemy is weak
time limit per test
5 seconds
memory limit per test
256 megabytes
input
standard input
output
standard output

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 ai>aj>ak where ax 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.

Input

The first line of input contains a single number n (3≤n≤106) − the number of men in Roman army. Next line contains n different positive integers ai (1≤in,1≤ai≤109) − powers of men in the Roman army.

Output

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).

Examples
Input
3
3 2 1
Output
1
Input
3
2 3 1
Output
0
Input
4
10 8 3 1
Output
4
Input
4
1 5 4 3
Output
1

题目来源:fps-www.educg.net-codeforce-1-2833.xml.zip;FPS 共享题包,题包内第 906 题。保留原作者与原赛事署名。