POJ 3481 Double Queue

#include<cstdio>
#include<cstdlib>
#include<set>
#include<utility>
using namespace std;
typedef pair<int,int> pii;
int main(){
    int op, k, p;
    set<pii> que;
    for(;;){
        scanf("%d", &op);
        if(op == 0) break;
        if(op == 1){
            scanf("%d %d", &k, &p);
            que.insert(pii(p, k));
        }else if(op == 2){
            if(que.size() == 0)
                puts("0");
            else{
                set<pii>::iterator get = que.end();
                get--;
                printf("%d\n", get->second);
                que.erase(*get);
            }
        }else{
            if(que.size() == 0)
                puts("0");
            else{
                set<pii>::iterator get = que.begin();
                printf("%d\n", get->second);
                que.erase(*get);
            }
        }
    }
    return 0;
}