后面超时了应该怎么改呢大佬们

#include<iostream>
#include<deque>
using namespace std;
int main()
{
	int  n;
	cin >> n;
	deque<int> q;
	int x;
	int flag = 0;
	for(int i = 0;i < n;i++)
	{
		cin >> x;
		if(x==0)
		{
			int y;
			cin>>y;
			q.push_back(y);
		}
		if(x==1)
		{
			q.pop_back();
		}
		if(x==2)
		{    
		    if(flag==1)
		       cout<<'\n';
		    int max=0;
			int z=q.size();
			if(z==0)
			{
				cout<<0;
			}
			else
			{
				max=q[0];
				for(int i=0;i<z;i++)
				{
					if(q[i]>max)
					{
						max=q[i];
					}
					
				}
				cout<<max;
			}
			flag=1;
			
		}
	}
	return 0;	
}