1246  inversion pair II
Time Limit : 3 Second
Memory Limit : 128 MB
Submission: 377
Solved: 84
 Description
 An pair ( i , j ) is called ‘inversion pair’ if and only if i < j and a[i] > a[j].
Given an integer sequence {a[i]} with N elements ( 1 <= N <= 100000 ), output the total number of inversion pairs.
A integer sequence like this : 2, 3, 1 has two inversion pairs.( 2, 1) and (3, 1)
 Input
 The input contains several test cases.
Each case begins with a number N ( 1 <= N <= 100000 ) , then N integers followed .  Output
 The number of the sequence's inversion pairs in the input.
 sample input

3 3 2 1 2 1 2
 sample output

3 0
 hint
 source