#include <bits/stdc++.h>
using namespace std;

int main(){
  int n;
  cin >> n;
  vector<int> ms(n,0);
  for(int i=0; i<n; ++i) cin >> ms[i];

  int count = 0;
  set<int> s;
  for(auto m : ms){
    count += distance(s.lower_bound(m), s.end());
    s.insert(m);
  }

  cout << count << endl;  
  return 0;
}