1 #include<iostream>
2 #include<stdio.h>
3 #define MAXN 500000
4 using namespace std;
5
6 int a[MAXN];
7 int c[MAXN];
8 long long n;
9 void Merge(int le, int mid, int rh);
10 void MergeSort(int le, int rh);
11 int main()
12 {
13 //freopen("acm.acm","r",stdin);
14 int num;
15 int i;
16 while(cin>>num && num)
17 {
18 n = 0;
19 for(i = 0; i < num; ++ i)
20 cin>>a[i];
21 MergeSort(0,num-1);
22 //for(i = 0; i < num; ++ i)
23 // cout<<a[i]<<" ";
24 //cout<<endl;
25 cout<<n<<endl;
26 }
27 }
28
29 void MergeSort(int le, int rh){
30
31
32 if (rh>le)
33 {
34 int mid = (le+rh) >> 1;
35 MergeSort(le,mid);
36 MergeSort(mid + 1,rh);
37 Merge(le, mid, rh);
38 }
39 }
40
41 void Merge(int le, int mid, int rh)
42 {
43 int i, j,p = 1;
44 for (i = le, j = mid+1; i <= mid && j <= rh; )
45 {
46 if (a[j] < a[i])
47 {
48 c[p++] = a[j++];
49 n += mid - i + 1;
50 }
51 else c[p++] = a[i++];
52 }
53 while ( j <= rh )
54 c[p++] = a[j++];
55 while( i <= mid )
56 c[p++] = a[i++];
57
58 for (i = le; i <= rh; ++i)
59 {
60 a[i] = c[i - le + 1];
61 }
62 }
