Something

 int mon_calcul() 
 {	
   int nb_a;
   int nb_b; 
   
        nb_a = 8;
        nb_b = 5;
        nb_a = nb_a + nb_b;
     return(nb_a);
  }
        
   int main()

      {
     int Calcul; 
  
     Calcul = mon_calcul();
      }