#include<iostream.h>
#include<stdlib.h>  //za da raboti exit(0)
#include<math.h>  //za da se polzva pow (stepen)

float suma(float a, float b, float c) {
 return a+b+c;
}

double proizv(float a, float b, float c) {
 return a*b*c;
}

float sredno (float a, float b, float c) {
 return (a+b+c)/3;
}

float sr_geom(float a, float b, float c) {
 return pow(a*b*c, 1/3.0);
}

void perimetar(float a, float b, float c) {
 if ((a+b>c)&&(b+c>a)&&(a+c>b))
    cout<<a+b+c<<endl;
 else cout<<"nqma takuv triagalnik"<<endl;
}

void lice(float a, float b, float c) {
 float p;
 if ((a+b>c)&&(b+c>a)&&(a+c>b))  {
    p=(a+b+c)/2;
    cout<<sqrt(p*(p-a)*(p-b)*(p-c))<<endl;                }
 else cout<<"nqma takuv triagalnik"<<endl;
}


int main(){
float a,b,c;
int choice;

 while(true){
 cout<<"vavedi 3 chisla: ";
 cin>>a>>b>>c;
 cout<<"Izberete dejstvie:"<<endl;
 cout<<"1.Subirane"<<endl;
 cout<<"2.Proizvedenie"<<endl;
 cout<<"3.Sredno aritmetichno"<<endl;
 cout<<"4.Sredno geometrichno"<<endl;
 cout<<"5.Perimetar na triagalnik"<<endl;
 cout<<"6.Lice na triagalnik"<<endl;
 cout<<"7.Izhod"<<endl;
 cin>>choice;
 switch (choice) {
  case 1: cout<<suma(a,b,c)<<endl; break;
  case 2: cout<<proizv(a,b,c)<<endl; break;
  case 3: cout<<sredno(a,b,c)<<endl; break;
  case 4: cout<<sr_geom(a,b,c)<<endl; break;
  case 5: perimetar(a,b,c); break;
  case 6: lice(a,b,c); break;
  case 7: exit(0);
  default: continue;
 }
 }

    return 0;
}