#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <queue>
#include <cmath>
#include <set>
#define fast_io cin.tie(NULL); cout.tie(NULL); ios_base::sync_with_stdio(false);
using namespace std;
typedef long long ll;

int n;
ll arr[500001];

ll merge(ll arr[], ll temp[], int left, int mid, int right){
    int i, j, k;
    ll inv_count = 0;
    i = left; j = mid; k = left;
    while (i<mid&&j<=right){
        if(arr[i]<=arr[j]){
            temp[k++] = arr[i++];
        }else{
            temp[k++] = arr[j++];
            //mid는 right덩어리의 처음 index이다. 
            inv_count += mid-i;
        }
    }
    //남은거 다 넣어
    while (i<mid) temp[k++] = arr[i++];
    while (j<=right) temp[k++] = arr[j++];
    //원래 배열로 다 옮겨
    for(i= left;i<=right;i++) arr[i] = temp[i];
    return inv_count;
}

ll _mergeSort(ll arr[], ll temp[], int left, int right){
    int mid; ll inv_count=0;
    if(right>left){
        mid = (left+right)>>1;
        inv_count += _mergeSort(arr, temp, left, mid);
        inv_count += _mergeSort(arr, temp, mid+1, right);

        inv_count += merge(arr, temp, left, mid+1, right);
    }
    return inv_count;
}

ll mergeSort(ll arr[], int array_size){
    ll temp[array_size];
    return _mergeSort(arr, temp, 0, array_size-1);  //mergesort call-by-address
}

int main(){
    fast_io;
    cin >> n;
    for(int i=0;i<n;i++) cin >> arr[i];
    cout << mergeSort(arr, n);
}