public class Bag {
    int[] a;
    //@ invariant a != null;
    int n;
    //@ invariant 0 <= n && n <= a.length;

    //@ requires initialElements != null;
    Bag(int[] initialElements) {
	n = initialElements.length;
	a = new int[n];
	System.arraycopy(initialElements, 0, a, 0, n);
    }

    Bag(int[] initialElements, int start, int howMany) {
	n = howMany;
	a = new int[n];
	for (int i=start; i<howMany; i++)
	  a[i] = initialElements[i];
    }

    int extractMin() {
	int m = Integer.MAX_VALUE;
	int mindex = 0;
	for (int i = 0; i < n; i++) {
	    if (a[i] < m) {
		mindex = i;
		m = a[i];
	    }
	}
	if (n > 0) {
	    n--;
	    a[mindex] = a[n];
	}
	return m;
    }

    void add(int x) {
	if (n == a.length) {
	    int[] b = new int[2*a.length];
	    System.arraycopy(a, 0, b, 0, n);
	    a = b;
	}
	a[n] = x;
	n++;
    }
}