#include "iostream"
#include "string"
#include "vector"
//#include "functional"
//#include "algorithm"
using namespace std;

class Operation
{
public:
	Operation(){}
	Operation(double dNumberA1, double dNumberB1)
	{
		dNumberA = dNumberA1;
		dNumberB = dNumberB1;
		dResult = 0.0;
	}
	double GetNumberA()
	{
		return dNumberA;
	}
	void SetNumberA(double dTempA)
	{
		dNumberA = dTempA;
	}
	double GetNumberB()
	{
		return dNumberA;
	}

	void SetNumberB(double dTempB)
	{
		dNumberB = dTempB;
	}

	virtual double GetResult()
	{
		return dResult;
	}
protected:
	double dNumberA;
	double dNumberB;
	double dResult;
};

class OperationAdd:public Operation
{
public:
	OperationAdd(){}
	OperationAdd(double dNumberA, double dNumberB):Operation(dNumberA, dNumberB){}
	double GetResult()
	{
		return dResult = dNumberA + dNumberB;
	}
};

class OperationSub:public Operation
{
public:
	OperationSub(){}
	OperationSub(double dNumberA, double dNumberB):Operation(dNumberA, dNumberB){}
	double GetResult()
	{
		return dResult = dNumberA - dNumberB;
	}
};

class OperationMul:public Operation
{
public:
	OperationMul(){}
	OperationMul(double dNumberA, double dNumberB):Operation(dNumberA, dNumberB){}
	double GetResult()
	{
		return dResult = dNumberA * dNumberB;
	}
};

class OperationDiv:public Operation
{
public:
	OperationDiv(){}
	OperationDiv(double dNumberA, double dNumberB):Operation(dNumberA, dNumberB){}
	double GetResult()
	{
		if (dNumberB == 0)
			throw runtime_error("除数不能为");
		return dResult = dNumberA / dNumberB;
	}
};

class OperationFactory
{
public:
	OperationFactory(string strOperaKind)
	{
		if (strOperaKind == "+")
			pOpera = new OperationAdd();
	    if (strOperaKind == "-")
			pOpera = new OperationSub();
		if (strOperaKind == "*")
			pOpera = new OperationMul();
		if (strOperaKind == "/")
			pOpera = new OperationDiv();	
	}
	Operation* GetOperation()
	{
		return pOpera;
	}
	~OperationFactory()
	{
		if (pOpera)
		{
			delete pOpera;
			pOpera = NULL;
		}
	}
private:
	Operation *pOpera;
};

int main() 
{
	cout << "Input two num and a operation(a number, opera, a number):" << endl;
	double dNumberA1, dNumberB1;
	string strOpera;
	cin >> dNumberA1 >> dNumberB1 >> strOpera;
    
	OperationFactory MyOperationFac(strOpera);
	Operation *MyOperation = MyOperationFac.GetOperation();
	MyOperation->SetNumberA(dNumberA1);
	MyOperation->SetNumberB(dNumberB1);
	cout << MyOperation->GetResult();
	return 1;
}