为什么会死递归，题目

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