class Strategy
{
public:
    Strategy(){}
    virtual ~Strategy(){}
    virtual int doOperation(int num1, int num2) = 0;
};

class OperationAdd : public Strategy
{
public:
    int doOperation(int num1, int num2)
    {
        return num1 + num2;
    }
};

class OperationSubstract: public Strategy
{
public:
    int doOperation(int num1, int num2)
    {
        return num1 - num2;
    }
};

class OperationMultiply: public Strategy
{
public:
    int doOperation(int num1, int num2)
    {
        return num1 * num2;
    }
};