#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#include <atcoder/fenwicktree>
struct dcin{template<typename T>dcin&operator>>(T&x){return std::cin>>x,x--,*this;}}dcin;

ll inversion_num(vector<ll> a){
    ll n = a.size(), res = 0;
    atcoder::fenwick_tree<ll> fw(n);
    for(ll i = n-1; i >= 0;i--){
        res += fw.sum(0,a[i]);
        fw.add(a[i],1);
    }
    return res;
}

int main(){
    ll n; cin >> n;
    vector<ll> a(n);
    for(ll &i : a)dcin >> i;
    cout << inversion_num(a) << endl;
}