private final static long MODULO = 1000 * 1000 * 1000 + 7;

    private void solve() {
        int n = readInt();

        int a = readInt();
        int b = readInt();

        LimitedQueueWithSum aQueue = new LimitedQueueWithSum(a);
        LimitedQueueWithSum bQueue = new LimitedQueueWithSum(b);

        aQueue.add(1);
        bQueue.add(1);

        for (int length = 2; length <= n; ++length) {
            long aSum = aQueue.getSum();
            long bSum = bQueue.getSum();

            aQueue.add(bSum);
            bQueue.add(aSum);
        }

        long answer = add(aQueue.getSum(), bQueue.getSum());
        out.println(answer);
    }

    static long add(long a, long b) {
        return (a + b) % MODULO;
    }

    static long subtract(long a, long b) {
        return add(a, MODULO - b % MODULO);
    }

    static class LimitedQueueWithSum {
        final int sizeLimit;

        Queue<Long> queue;
        long sum;

        LimitedQueueWithSum(int sizeLimit) {
            this.sizeLimit = sizeLimit;

            queue = new ArrayDeque<>();
            sum = 0;
        }

        void add(long value) {
            queue.add(value);
            sum = Problem2018.add(sum, value);

            if (queue.size() > sizeLimit) {
                long removed = queue.poll();
                sum = subtract(sum, removed);
            }
        }

        long getSum() {
            return sum;
        }
    }