/**
 * Returns a^b, as the standard mathematical exponentiation function
 */
 double pow(double a, int b) {
    bool neg = b < 0;
    b = abs(b);
    double result = 1;
    while (b > 0) {
        if (b%2 == 1) {
            result *= a;
            --b;
        }
        a *= a;
        b /= 2;
    }
    if (neg) return 1/result;
    return result;
}



public interface TwoSum {

    private ArrayList<Integer> elems;
    private HashMap<Integer, Integer> count;

    public TwoSum() {
        elems = new ArrayList();
        count = new HashMap();
    }


    /**
     * Stores @param input in an internal data structure.
     */
    void store(int input) {
        elems.add(input);
        if (count.contains(input)) {
            int e = count.get(input);
            cout.set(input,e+1);
        } else {
            count.set(input,1);
        }
    }

    /**
     * Returns true if there is any pair of numbers in the internal data structure which
     * have sum @param val, and false otherwise.
     * For example, if the numbers 1, -2, 3, 6, and 6 had been stored,
     * the method should return true for 4, -1, and 9, but false for 10, 5, and 0
     */
    boolean test(int val) {
        for (int e : elems) {
            int search = val - e;
            int c = count.get(search);
            if (c == null) {
                continue;
            } else {
                if (search == e && c > 1) {
                        return true;
                    }
                } else {
                    return true;
                }
            }
        }
         return false;
    }
}