#include <iostream>
#include <algorithm>
#include <map>
#include <stack>
#include <queue>
#include <string.h>
#include <vector>
#include <math.h>
#include <stdio.h>
using namespace std;
const int N = 500010;
int n, ans, tot, a[N], c[N], k[N];
map<int, int> dis;
void Dis() {
    dis.clear(), tot = 0;
    memcpy(k, a, sizeof a);
    sort(k+1, k+1+n);
    ans = 0;
    for (int i = 1; i <= n; ++i) {
        if (!dis[k[i]]) {
            dis[k[i]] = ++tot;
        }
        c[i] = 0;
    }
    for (int i = 1; i <= n; ++i) {
        a[i] = dis[a[i]];
    }
}
int lowBit(int x) {
    return x & -x;
}
int sum(int x) {
    int res = 0;
    for (; x; x -= lowBit(x)) {
        res += c[x];
    }
    return res;
}
void add(int x, int y) {
    for (; x <= n; x += lowBit(x)) {
        c[x] += y;
    }
}
int main() {
    while (scanf("%d", &n), n) {
        for (int i = 1; i <= n; ++i) {
            scanf("%d", &a[i]);
        }
        Dis();
        for (int i = n; i >= 1; --i) {
            ans += sum(a[i]-1);
            add(a[i], 1);
        }
        printf("%d\n", ans);
    }
    return 0;
}

为什么这个树状数组代码在vjudge上回T掉？求大佬指点！！！