include[HTML_REMOVED]
using namespace std;
const int N = 1e6 + 10;
int a[N];
int q[N];
int n, m;
double h;
void quick_sort(int l, int r) {
if (l >= r) return;
int mid = l + r >> 1;
quick_sort(l, mid);
quick_sort(mid + 1, r);
int i = l, j = mid + 1, k = 0;
while (i <= mid && j <= r) {
if (a[i] <= a[j]) q[k] = a[i];
else {
h += mid - i + 1;//逆序对数量 当a[i]比a[j]大时 a[i]后面的数一定比a[j]大 所以是mid-i+1
q[k] = a[j];
}
}
while (i <= mid) q[k] = a[i];
while (j <= r) q[k] = a[j];
for (int i = l, j = 0; i <= r; i++, j++)
a[i] = q[j];
}
int main() {
scanf(“%d”, &n);
for (int i = 0; i < n; i++) {
scanf(“%d”, &a[i]);
}
quick_sort(0, n - 1);
printf(“%.0lf”, h);
return 0;
}