Tower of hanoi In groovy

hanoi.groovy

def main() {
    def reader = new Scanner(System.in)
    int a = reader.nextInt()
    BigInteger count = (2 ** a) -1
    println(count)
    boolean canPrint = a <= 20

    def hanoiTower
    hanoiTower = { int num, int from, int to, int aux ->

        if (num == 1) {
            System.out.printf("%d %d\n",from ,to)
            return
        }
        hanoiTower(num - 1, from, aux, to)
        System.out.printf("%d %d\n",from ,to)
        hanoiTower(num - 1, aux, to, from)
    }
    if(canPrint) {
        hanoiTower.call(a, 1, 3, 2)
    }
}