import com.google.gson.*;

interface DecisionTree{}

class Leaf implements DecisionTree{
	int h;

	Leaf(int val){
		h = val;
	}
}

class Compound implements DecisionTree{
	int q;
	DecisionTree y;
	DecisionTree n;

	Compound(int q,DecisionTree y,DecisionTree n){
		this.q = q;
		this.y = y;
		this.n = n;
	}
}

class DecisionTreeHead{
	DecisionTree decisiontree;
	
	DecisionTreeHead(DecisionTree dt){
		decisiontree = dt;
	}
}

public class DTTest{
	public static void main(String[] args){
		DecisionTree L0 = new Leaf(0);
		DecisionTree L1 = new Leaf(1);
		DecisionTree L2 = new Leaf(2);
		DecisionTree L3 = new Leaf(3);
		DecisionTree C3 = new Compound(3,L2,L3);
		DecisionTree C2 = new Compound(2,L1,C3);
		DecisionTree C1 = new Compound(1,L0,C2);
		DecisionTreeHead dt = new DecisionTreeHead(C1);
		
		Gson gs = new Gson();
		System.out.println(gs.toJson(dt));
	}
}