C++ :

#include <iostream>
#include <cstdio>
using namespace std;

const int N = 10010;
int n, a[N], q[N], cnt;

void msort(int l, int r) {
	if (l == r) return;
	
	int mid = l + r >> 1;
	int i = l, j = mid + 1, k = l;
	
	msort(i, mid);
	msort(j, r);
	
	while (i <= mid && j <= r) {
		if (a[i] <= a[j]) {
			q[k++] = a[i++];
		}
		else {
			q[k++] = a[j++];
			cnt += mid - i + 1;
		}
	}
	
	while (i <= mid) {
		q[k++] = a[i++];
	}
	while (j <= r) {
		q[k++] = a[j++];
	}
	
	for (int i = l; i <= r; i ++) {
		a[i] = q[i];
	}	
}

int main() {
	cin >> n;
	for (int i = 1; i <= n; i ++) cin >> a[i];
	
	msort(1, n);
	
	cout << cnt;

	return 0;
}