1 #include<iostream>
2 #include<malloc.h>
3 using namespace std;
4 long long ans;
5 void merge(int *a,int le,int mid,int rt){
6 int *sort_data=(int *)malloc(sizeof(int)*(rt-le+1));
7 if(!sort_data) return;
8 int i=le,j=mid+1,pt=0;
9 while(i<=mid&&j<=rt){
10 if(a[i]<=a[j]){
11 sort_data[pt++]=a[i++];
12 }
13 else{//exist swap action
14 sort_data[pt++]=a[j++];
15 /*
16 once we swap the postion of both the a[i] and a[j],
17 we do change the positon of a[i+1......mid]
18 so as a result, we do change the postion of a[i,i+1,....mid].
19 */
20 ans+=mid-i+1;
21 }
22 }
23 while(i<=mid){
24 sort_data[pt++]=a[i++];
25 }
26 while(j<=rt){
27 sort_data[pt++]=a[j++];
28 }
29 int p;
30 for(int i=le,p=0;i<=rt;i++,p++){
31 a[i]=sort_data[p];
32 }
33 }
34 void mergeSort(int a[],int st,int ed){
35 if(st<ed){
36 int mid=(st+ed)/2;
37 mergeSort(a,st,mid);
38 mergeSort(a,mid+1,ed);
39 merge(a,st,mid,ed);
40 }
41 }
42 int main(){
43 int n,num[500010];
44 while(scanf("%d",&n),n){
45 ans=0;
46 for(int i=0;i<n;i++){
47 scanf("%d",&num[i]);
48 }
49 mergeSort(num,0,n-1);
50 printf("%I64d\n",ans);
51 }
52 return 0;
53 }
