Poj 2299 Ultra-QuickSort

#include <stdio.h>
#include <limits.h>

long long Count = 0;
const int MAX_N = 500000 + 10;
long long A[MAX_N], L[MAX_N], R[MAX_N];

void Merge(long long A[], int p, int q, int r)
{
    int i, j, k;

    int n1 = q - p + 1;
    int n2 = r - q;

    for (int i = 0; i < n1; ++i)
        L[i] = A[p + i];
    for (int j = 0; j < n2; ++j)
        R[j] = A[q + j + 1];

    i = j = 0;
    k = p;
    L[n1] = INT_MAX;
    R[n2] = INT_MAX;

    while (k <= r)
    {
        if (L[i] > R[j])
        {
            A[k++] = R[j++];
            Count += n1 - i;
        }
        else
            A[k++] = L[i++];
    }
}

void Merge_Sort(long long A[], int p, int q)
{
    int r = (p + q) / 2;

    if (p < q)
    {
        Merge_Sort(A, p, r);
        Merge_Sort(A, r + 1, q);
        Merge(A, p, r, q);
    }
}

int main()
{
    int n;

    while (scanf("%d", &n) == 1)
    {
        if (n == 0)
            break;

        Count = 0;

        for (int i = 0; i < n; ++i)
            scanf("%d\n", &A[i]);

        Merge_Sort(A, 0, n - 1);
        printf("%lld\n", Count);
    }

    return 0;
}