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SGU 180 解题报告

http://acm.sgu.ru/problem.php?contest=0&problem=180

180. Inversions

time limit per test: 0.50 sec.
memory limit per test: 4096 KB

There are N integers (1<=N<=65537) A1, A2,.. AN (0<=Ai<=10^9). You need to find amount of such pairs (i, j) that 1<= i < j <= N and A[i]>A[j].

Input

The first line of the input contains the number N. The second line contains N numbers A1...AN.

Output

Write amount of such pairs.

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