1 #include <bits/stdc++.h>
2 using namespace std;
3 #define _for(i,a,b) for(int i = (a);i < b;i ++)
4 const int maxn = 500009;
5 typedef long long ll;
6 int n;
7 ll a[maxn],c[maxn];
8 ll ans = 0;
9 inline ll read()
10 {
11 ll ans = 0;
12 char ch = getchar(), last = ' ';
13 while(!isdigit(ch)) last = ch, ch = getchar();
14 while(isdigit(ch)) ans = (ans << 1) + (ans << 3) + ch - '0', ch = getchar();
15 if(last == '-') ans = -ans;
16 return ans;
17 }
18 inline void write(ll x)
19 {
20 if(x < 0) x = -x, putchar('-');
21 if(x >= 10) write(x / 10);
22 putchar(x % 10 + '0');
23 }
24 void msort(int le,int rr)
25 {
26 if(le==rr)
27 return ;
28 int mid = (le+rr)/2;
29 msort(le,mid),msort(mid+1,rr);
30 int i = le,j = mid+1;
31 int k = le;
32 while(i <= mid && j <= rr)
33 {
34 if(a[i]<=a[j])
35 c[k++] = a[i++];
36 else
37 {
38 c[k++] = a[j++];
39 ans += mid-i+1;
40 }
41 }
42 memcpy(c+k,a+i,(mid-i+1)*(sizeof(ll)));
43 k += mid-i+1;
44 memcpy(c+k,a+j,(rr-j+1)*(sizeof(ll)));
45 memcpy(a+le,c+le,(rr-le+1)*(sizeof(ll)));
46 }
47 int main()
48 {
49 n = read();
50 _for(i,0,n)
51 a[i] = read();
52
53 msort(0,n-1);
54 write(ans);
55 return 0;
56 }
