#include <iostream>
#include <vector>
using namespace std;
//归并的时候 如果交换顺序逆序对++
long long ans = 0;
void merge(vector<int>& arr, int l, int r){
    int mid = l + (r-l)/2;
    vector<int> tmp;
    int i = l, j = mid+1;
    while(i <= mid && j <= r){
        if(arr[i] <= arr[j]){
            tmp.push_back(arr[i]);
            i++;
        } else {
            tmp.push_back(arr[j]);
            j++;
            ans += mid-i+1;
        }
    }
    while (i <= mid) {
        tmp.push_back(arr[i]);
        i++;
    }
    while (j <= r) {
        tmp.push_back(arr[j]);
        j++;
    }
    for(int i = l; i <= r; i++){
        arr[i] = tmp[i-l];
    }
}
void mergesort(vector<int>& arr, int l, int r){
    if(l >= r) return;
    int mid = l + (r-l)/2;
    mergesort(arr, l, mid);
    mergesort(arr, mid+1, r);
    
    merge(arr, l, r);
}
//辅助函数

int main(){
    int n;
    cin >> n;
    vector<int> arr(n);
    for(int i = 0; i < n; ++i){
        cin >> arr[i];
    }
    mergesort(arr,0, arr.size()-1);
    /*for(auto x: arr){
        cout << x << " ";
        } cout << endl;*/
    cout << ans << endl;
    return 0;
}