#include<string>

template <class T>
class Classsy
{
public:
    Classsy(T x) {
        this->x = x;
    }
    void doSomething() {
        std::cout << doSomething(x) << std::endl;
    }

private:
    <template class T> T doSomething(T arg) {
        return arg+arg;
    }

    T x;
};

int main(int argc, char const *argv[]) {
    Classsy <int> kupa(5);
    Classsy <std::string> dupa("sdsd");
    kupa.doSomething();
    dupa.doSomething();

    return 0;
}