RE 0求助

RT

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll N=1e6+1;
ll c[N];//树状数组 
inline ll lowbit(ll x){
    return x&-x;
}
inline void updata(ll x,ll y){
    for (;x<N;x+=lowbit(x))
        c[x]+=y;
}
inline ll query(ll len){
    ll res=0;
    for (;len;len-=lowbit(len))
        res+=c[len];
    return res; 
} 
ll n;
ll ans=0;
ll num;
int main(){
    scanf("%lld",&n);
    for (ll i=1;i<=n;i++){
        scanf("%lld",&num);
        updata(num,1);
        ans+=i-query(num);
    }
    printf("%lld\n",ans);
}