1 #include<iostream>
 2 #include<cstdio>
 3 using namespace std;
 4 int a[50020],b[50020];
 5 int n;
 6 long long merge(int low,int mid,int high){
 7     int i=low,j=mid+1,k=low;
 8     long long count=0;
 9     while(i<=mid&&j<=high){
10         if(a[i]<=a[j]){
11             b[k++]=a[i++];
12         }
13         else{
14             b[k++]=a[j++];
15             count+=j-k;
16         }
17     }
18     while(i<=mid){
19         b[k++]=a[i++];
20     }
21     while(j<=high){
22         b[k++]=a[j++];
23     }
24     for(i=low;i<=high;i++){
25         a[i]=b[i];
26     }
27     return count;
28 }
29 long long mergeSort(int x,int y){
30     
31     if(x<y){
32         int mid=(x+y)/2;
33         long long count=0;
34         count+=mergeSort(x,mid);
35         count+=mergeSort(mid+1,y);
36         count+=merge(x,mid,y);
37         return count;
38     }
39     return 0;
40 }
41 int main(){
42     cin>>n;
43     for(int i=0;i<n;i++){
44         scanf("%d",&a[i]);
45     }
46     cout<<mergeSort(0,n-1);
47     return 0;
48 }