#include <fstream>
#include <vector>

using namespace std;

unsigned long long main_merge(vector<int> &arr, vector<int> &temp, int left, int right);

unsigned long long merge(vector<int> &arr, vector<int> &temp, int left, int mid, int right);

unsigned long long merge_sort(vector<int> &arr, int array_size) {

    vector<int> temp(arr.size());
    return main_merge(arr, temp, 0, array_size - 1);
}

unsigned long long main_merge(vector<int> &arr, vector<int> &temp, int left, int right) {

    unsigned long long mid, inv_count = 0;

    if (right > left) {
        mid = (right + left) / 2;
        inv_count = main_merge(arr, temp, left, mid);
        inv_count += main_merge(arr, temp, mid + 1, right);
        inv_count += merge(arr, temp, left, mid + 1, right);
    }

    return inv_count;
}

unsigned long long merge(vector<int> &arr, vector<int> &temp, int left, int mid, int right) {
    int i, j, k;
    unsigned long long inv_count = 0;
    i = left;
    j = mid;
    k = left;

    while ((i <= mid - 1) && (j <= right)) {

        if (arr[i] <= arr[j]) {
            temp[k++] = arr[i++];
        } else {
            temp[k++] = arr[j++];
            inv_count = inv_count + (mid - i);
        }
    }

    while (i <= mid - 1)
        temp[k++] = arr[i++];

    while (j <= right)
        temp[k++] = arr[j++];

    for (i = left; i <= right; i++)
        arr[i] = temp[i];

    return inv_count;
}

int main() {

    ifstream in("input.txt");
    ofstream out("output.txt");

    int n;
    in >> n;
    vector<int> arr(n);

    for (int i = 0; i < n; i++) {
        in >> arr[i];
    }
    out << merge_sort(arr, arr.size());
}