Функция минимума

#include <iostream>
 
using namespace std;
 
double Z (double _a, double _b)
{
    return min(_a , 3 *_b) * min(2 * _a - _b, 2 * _b);
}
 
int main()
{
   double a,b;
 
   cout <<"Vvedite a = ";
   cin >> a;
 
   cout << "Vvedite b = ";
   cin >> b;
 
   cout << endl;
 
   cout << "Z(" << a <<"," << b <<")=" << Z(a,b) << endl;
    return 0;
}

#include <iostream>
 
using namespace std;
 
double MIN_ (double a_, double b_)
{
  if(a_ > b_) return b_;
  else return a_;
}
 
double ZZ (double _aa, double _bb)
{
    return MIN_(_aa , 3 *_bb) * MIN_(2 * _aa - _bb, 2 * _bb);
}
 
 
 
int main()
{
   double a,b;
 
   cout <<"Vvedite a = ";
   cin >> a;
 
   cout << "Vvedite b = ";
   cin >> b;
 
   cout << endl;
 
   cout << "ZZ(" << a <<"," << b <<")=" << ZZ(a,b) << endl;
    return 0;
}