#include <string>       // std::string
#include <iostream>     // std::cout
#include <sstream>      // std::stringstream
#include <vector>
#include <string>

using namespace std;


class Relation 
{
	string name;
	
	public:
	
	string getName()
	{
		return name;
	}
}



class Union
{
	string Un1;
	string Un2;
	
	Union (string s1, string s2)
	{
		Un1 = s1;
		Un2 = s2;
	}
	
	string getUnion()
	{
		return "Union of " + Un1 + " and " + Un2;
	}
}

class Product
{
	string Pr1;
	string Pr2;
	
	Product(string s1, string s2)
	{
		Pr1 = s1;
		Pr2 = s2;
	}
	
	string getProduct()
	{
		return "Product of " + Pr1 + " and " + Pr2;
	}
}

class Difference()
{
	string D1;
	string D2;
	
	Difference(string s1, string s2)
	{
		D1 = s1;
		D2 = s2;
	}
	
	string getDifference()
	{
		return "Difference of " + D1 + " and " + D2;
	}
}

class Rename()
{
	string newName;
	string oldName;
	
	Rename(string s1, string s2)
	{
		newName = s1;
		oldName = s2;
	}
	
	string doRename()
	{
		return "Renaming " + oldName + " to " + newName;
	}
}

class Projection()
{
	string newName;
	string oldName;
	
	Rename(string s1, string s2)
	{
		newName = s1;
		oldName = s2;
	}
	
	string doRename()
	{
		return "Projecting " + oldName + " onto " + newName;
	}
}

class Operand()
{
	string op;
	
	Operand(string str)
	{
		op = str;
	}
	
	void setOperand(string str)
	{
		op = str;
	}
	
	string getOperand()
	{
		return op;
	}
}

class Op()
{
	string op;
	
	Op(string str)
	{
		op = str;
	}
	
	void setOp(string str)
	{
		op = str;
	}
	
	string getOp()
	{
		return op;
	}
}

class Comparison()
{
	Op op;
	Operand operand1;
	Operand operand2;
	
	Comparison(string str1, string str2, string str3)
	{
		operand1.setOperand(str1);
		op.setOp(str2);
		operand2.setOperand(str3);
	}
	
	void setComparison(string str1, string str2, string str3)
	{
		operand1.setOperand(str1);
		op.setOp(str2);
		operand2.setOperand(str3);
	}
	
	string getComparison()
	{
		return op1.getOperand() + " " + op.getOp() + " " + op2.getOperand();
	}
}

class Conjunction()
{
	string conj;
	
	Conjunction(string str)
	{
		conj = str;
	}
	
	void setConjunction(string str)
	{
		conj = str;
	}
	
	string getConjunction()
	{
		return conj;
	}
}

class Condition()
{
	string cond;
	
	Condition(string str)
	{
		cond = str;
	}
	
	void setCondition(string str)
	{
		cond = str;
	}
	
	string getCondition()
	{
		return cond;
	}
}

class Selection()
{
	string select;
	
	Selection(string str)
	{
		select = str;
	}
	
	string getSelection()
	{
		return select;
	}
}

class expr
{
	Relation r;
	
	selection
    projection
    renaming
	Union
	difference
    product

}