D

#define _CRT_SECURE_NO_DEPRECATE

#include <iostream>
#include <vector>
#include <string>
#include <map>
#include <set>
#include <algorithm>

using namespace std;

long long cnt;
vector<int> a, c;
void mergesort(int l, int r)
{
	int mid;
	if (l < r)
	{
		mid = (l + r) / 2;
		mergesort(l, mid);
		mergesort(mid + 1, r);
		merge(l, r, mid);
	}
	return;
}

void merge(int l, int r, int m)
{
	long long i = l , j = m + 1, k = l;
	while (i <= m && j <= r)
	{
		if (a[i] <= a[j])
		{
			c[k++] = a[i++];
		}
		else
		{
			c[k++] = a[j++];
			cnt += (long long)m - i + 1LL;
		}
	}
	while (i <= m)
	{
		c[k++] = a[i++];
	}
	while (j <= r)
	{
		c[k++] = a[j++];
	}
	for (i = l; i < k; i++)
	{
		a[i] = c[i];
	}
}

int main() {
	freopen("input.txt", "r", stdin);
	freopen("output.txt", "w", stdout);

	int n;
	cin >> n;
	cnt = 0;
	a.resize(n);
	c.resize(n);
	for (int i = 0; i < n; i++)
	{
		cin >> a[i];
	}
	mergesort(0, n - 1);

	cout << cnt;

}