#include <queue>
using namespace std;
int main()
{
    queue<int> q; // presentation of queue
    q.push(5); // add 5 at the end of queue in O(1)
    q.pop(); // pop from front of queue in O(1)
    q.front(); // front of queue given in O(1)
    q.back(); // back of queue given in O(1)
    q.size(); // size of queue given in O(1)
    q.empty(); // if queue is empty, true otherwise false given in O(1)
    // in c++11
    queue<int> p;
    q.swap(p); //swap two queues in O(1)    
    return 0;
}