#include <iostream>

using namespace std;

class prostokat{
private:
    double a;
    double b;
    friend  void pole(prostokat p);
    friend void obwod(prostokat p);
public:
    prostokat(double a_,double b_);


};

prostokat::prostokat(double a_,double b_){
    a=a_;
    b=b_;


}

void pole(prostokat p){

cout << p.a*p.b << endl;

}


void obwod(prostokat p){

cout << p.a*2+p.b*2 << endl;

}

class trojkat{
private:
    double a;
    double b;
    double c;
    double h;
    friend  void pole(trojkat p);
    friend void obwod(trojkat p);
public:
    trojkat(double a_,double b_, double c_, double h_);
};

trojkat::trojkat(double a_,double b_, double c_, double h_){
    if(a<b+c){
        cout<< "to nie trojkat";

    }
    else if(b<c+a){
        cout<< "to nie trojkat";

    }
    else if(c<b+a){
        cout<< "to nie trojkat";

    }
    else{
        a=a_;
        b=b_;
        c=c_;
        h=h_;

    }
}
void pole(trojkat p){

cout << (p.h*p.a)/2<< endl;

}


void obwod(trojkat p){

cout <<a+b+c << endl;

}

int main()
{
    prostokat p1(10,2);
    pole(p1);
    cout << "Hello world!" << endl;
    return 0;
}