For Java 7.

import java.util.Scanner; import java.util.Stack;

class Queue { Stack getIn = new Stack<>(); Stack getOut = new Stack<>(); int size = 0;

Queue() {}

public int size() {
    return size;
    // This cause i update size when enqueue and dequeue already
    // Of course, you can just do:  getIn.size() + getOut.size()
}

public boolean isEmpty() {
    return size == 0;
}

public void Enqueue(int value) {
    getIn.add(value);
    size++;

    // First, item will be contain in getIn. More detail on Dequeue.
}

public int Dequeue() {
    if (getOut.size() == 0) {
        int n = getIn.size();
        for (; n > 0; n--) {
            getOut.add(getIn.pop());
        }
    }
    size--;
    return getOut.pop();

    // If getOut is empty, we can take nothing out from it. So, check for more item from getIn
    // Notice: never push from getIn to getOut while getOut is not Empty. It'll break the order
}

public int peek() {
    if (getOut.size() == 0) {
        int n = getIn.size();
        for (; n > 0; n--) {
            getOut.add(getIn.pop());
        }
    }
    return getOut.peek();

    // Similar to dequeue
}

}

public class Solution { public final static Scanner sc = new Scanner(System.in);

public static void main(String[] args) {
    int q = sc.nextInt();

    int ops;
    int newValue;
    Queue queue = new Queue();
    for (; q>0; q--) {
        ops = sc.nextInt();
        switch(ops) {
            case 1: // Enqueue
                newValue = sc.nextInt();
                queue.Enqueue(newValue);
                break;
            case 2: // Dequeue
                queue.Dequeue();
                break;
            case 3: // peek and print
                System.out.println(queue.peek());
                break;
            default:
        }
    }

    sc.close();
}