plostinaKrug

#include <iostream>

float plostinaKrug (float);

const float PI=3.14;
int main()
{
    float r;
    std::cout<<"Vnesi go radiusot na krugot: ";
    std::cin>>r;

    float n=plostinaKrug(r);

     std::cout<<"Ploshtinata e: "<<n;
    return 0;
}
 float plostinaKrug(float r)
{

   return r*r*PI;
}