娘的，自己的求逆序对模板又不好使了。。。。。。。。

#include<stdio.h>

long long cnt;
long long  a[500001],t[500001];

void merge(long long *a,long long *t,int l,int m,int r)
{
    int p = l;
    int q = m+1;
    int k = p;
    while(p <= m||q <= r)
    {
        if(q > r||(p <= m&&a[p] <= a[q]))
            t[k++] = a[p++];
        else
        {
            cnt += m-p+1;
            t[k++]=a[q++];
        }
    }
    for(int i = l; i <= r; i++)a[i]=t[i];
}
void mergesort(long long *a,long long *t,int l,int r)
{
    if(r > l)
    {
        int m = (l+r)/2;
        mergesort(a,t,l,m);
        mergesort(a,t,m+1,r);
        merge(a,t,l,m,r);
    }
}
int main()
{
    int n;
    while(~scanf("%d", &n))
    {
        if(n==0)
            break;
        cnt = 0;
        for(int i = 0; i < n; i++)
            scanf("%lld", &a[i]);
        mergesort(a,t,0,n-1);
        printf("%lld
", cnt);
    }
    return 0;
}