#include <bits/stdc++.h>
using namespace std;
int main() {
	int n,a,b;
	int q,s,p;
	while(cin>>n){
	queue<int> Q;
	stack<int> S;
	priority_queue<int> P;
		q=1;
		s=2;
		p=3;
		while(n--){
			cin>>a>>b;
			if(a==1){
				Q.push(b);
				S.push(b);
				P.push(b);
			}
			else if(a==2){
				if(Q.front()!=b)q=0;
				else Q.pop();
				if(S.top()!=b)s=0;
				else S.pop();
				if(P.top()!=b)p=0;
				else P.pop();
			}
		cout<<q<<" "<<p<<" "<<s<<endl;
 
		}
		int ans=max( max(q,p) , s);
			if(!ans)cout<<"impossible"<<endl;
			else if((q&&p)||(q&&s)||(s&&p)||(q&&p&&s))cout<<"not sure"<<endl;
			else if(q)cout<<"queue"<<endl;
			else if(s)cout<<"stack"<<endl;
			else if(p)cout<<"priority queue"<<endl;
	}
	return 0;
}

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

NgoxIDEKMSAyCjEgMwoyIDMKMiAyCjIgMQoyCjEgMQoyIDI=

6
1 1
1 2
1 3
2 3
2 2
2 1
2
1 1
2 2