为何输入8就超时,问题在7,8行

#include<bits/stdc++.h>
using namespace std;
int n,result_n,k=0;
vector<long long>apple;
void pick(int day){
	if(apple.size()>0){
		int a=(apple.size());
		for(int j=0;j<a;j=j+3){ 
			apple.erase(apple.begin()+j);
			if(j==n){
				result_n=j;
			}
		}
		sort(apple.begin(),apple.end());
		for(int j=0;j<apple.size();j++){ 
			cout<<apple[j]<<' ';
		}
		cout<<endl;
		pick(day+1);
	}
	else{
		cout<<result_n<<' '<<day;
	}
}
int main(){
	cin>>n;
	for(long long i=1;i<=n;i++){
		apple.push_back(i);
	}
	pick(0);
	return 0;
}