#include <iostream>
using namespace std;

using uint = unsigned int;

class Pog 
{
private:
    float first;
    uint second;
public:
    Pog(float a0, uint d)
    {
        this->first = a0;
        this->second = d;
    }
    float operator()(uint j)
    {
        return this->first + this->second * (j - 1);
    }
};

int main()
{
    float a0 = 2.5f;
    uint d = 5, j = 2;
    
    Pog pg(a0, d);
    cout << pg(j);
    
    return 0;
}