import java.io.*;

//====================================================================
//                     Class Expression
//====================================================================


abstract class Expression
{
    //---------------------------------------------------------------
    // simplify() returns a possibly simplified version of this 
    // expression.
    //---------------------------------------------------------------

    public abstract Expression simplify();

    //---------------------------------------------------------------
    // toString() returns a string that described this expression.
    // It can be used for printing this expression.
    //---------------------------------------------------------------

    public abstract String toString();

    //---------------------------------------------------------------
    // rawderiv() returns the derivative of this expression, without
    // simplification.
    //---------------------------------------------------------------

    public abstract Expression rawderiv();

    //---------------------------------------------------------------
    // deriv() returns the derivative of this expression, with
    // simplification.
    //---------------------------------------------------------------

    public Expression deriv()
    {
	return rawderiv().simplify();
    }
}

//====================================================================
//                     Class ConstantExpression
//====================================================================
// A constant expression is the expression equivalent of a real number.
//====================================================================

class ConstantExpression extends Expression
{
    private double value;

    public ConstantExpression(double v)
    {
	value = v;
    }

    public Expression rawderiv()
    {
	return new ConstantExpression(0.0);
    }

    public Expression simplify()
    {
	return this;
    }

    public String toString()
    {
	return "" + value;
    }

    public double getvalue()
    {
	return value;
    }
}

//====================================================================
//                     Class VarExpression
//====================================================================
// A VarExpression is the independent variable x.
//====================================================================

class VarExpression extends Expression
{
    public VarExpression()
    {
    }

    public Expression rawderiv()
    {
	return new ConstantExpression(1.0);
    }

    public Expression simplify()
    {
	return this;
    }

    public String toString()
    {
	return "x";
    }

}

//====================================================================
//                    Class SumExpression
//====================================================================
// A SumExpression is an expression that is the sum of two other
// expressions.
//====================================================================

class SumExpression extends Expression
{
    private Expression addend1, addend2;

    public SumExpression(Expression e1, Expression e2)
    {
	addend1 = e1;
	addend2 = e2;
    }

    public Expression rawderiv()
    {
	return new SumExpression(addend1.rawderiv(), addend2.rawderiv());
    }

    public Expression simplify()
    {
	return simplifySum(addend1.simplify(), addend2.simplify());
    }

    public String toString()
    {
	return "(" + addend1.toString() + "+" + addend2.toString() + ")";
    }

    private static Expression simplifySum(Expression e1, Expression e2)
    {
	// 0 + x = x and constant arithmetic

	if(e1 instanceof ConstantExpression) {
	    ConstantExpression ce = (ConstantExpression) e1;

	    // 0 + x = x

	    if(ce.getvalue() == 0.0) {
		return e2;
	    }

	    // Constant arithmetic 

	    if(e2 instanceof ConstantExpression) {
	      ConstantExpression ce2 = (ConstantExpression) e2;
	      return new ConstantExpression(ce.getvalue() + ce2.getvalue());
	    }
	}

	// x + 0 = x

	if(e2 instanceof ConstantExpression) {
	    ConstantExpression ce = (ConstantExpression) e2;
	    if(ce.getvalue() == 0.0) {
		return e1;
	    }
	}

	// Default: do not simplify.

	return new SumExpression(e1, e2);

    }
}