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void push_back_pb(deque<int> &dq, int x){

    dq.push_back(x);

}

/* Function to pop element from back
* dq : dqueue From which element is to be popped
*/
void pop_back_ppb(deque<int> &dq){

    if(!dq.empty())
     dq.pop_back();
    else
    return;

}

/* Function to return element from front
* dq : dqueue from which element is to be returned
*/
int front_dq(deque<int> &dq){

if(!dq.empty())
    return dq.front();
    else
    return -1;

}

/* Function to push element to front
* dq : dqueue in which element is to be pushed
* x : element to be pushed
*/
void push_front_pf(deque<int> &dq, int x){

    dq.push_front(x);

}