提交记录TLE

MY TLE code：

#include<iostream>
#include<cstdio>
#include<cmath>
#include<algorithm>
using namespace std;
const int N=5e5+5;
int n,ans;
int a[N],r[N];
void gsort(int s,int t) {
	if(s>=t) return;
	int mid=(s+t)/2;
	gsort(1,mid);
	gsort(mid+1,t);
	int i=s,j=mid+1,k=s;
	while(i<=mid&&j<=t) {
		if(a[i]<=a[j]) r[k++]=a[i++];
		else {
			r[k++]=a[j++];
			ans+=mid-i+1;
		}
	}
	while(i<=mid) r[k++]=a[i++];
	while(j<=t) r[k++]=a[j++];
	for(int i=s; i<=t; i++)
		a[i]=r[i];
}
int main() {
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	cin>>n;
	for(int i=1; i<=n; i++) cin>>a[i];
	gsort(1,n);
	cout<<ans<<endl;
	return 0;
}