Que dia de la semana es? C++

#include <stdio.h>
#include <stdlib.h>
#include <math.h>



main ()
{
     int H,Q,M,K,J,A; // DONDE H ES ES EL DIA DE LA SEMANA 0-7
     printf ("\n Ingrese el numero del dia  ");
     scanf ("%d", &Q); //Nº DEL DIA
     printf ("\n Ingrese el numero del mes \n Conciderando que Enero y febrero son los meses 13 y 14 del ano anterior  ");
     scanf ("%d", &M); // Nº MES
     printf ("\n Ingrese el numero del ano en que se encuentra  ");
     scanf ("%d", &A); // AÑO
    
     J = A/100;
     K = A%100;
    
     H = (Q+ ((26*(M+1))/10) + K + (K/4) + (J/4) + (5*J))%7; 
    // DONDE H ES LA FORMULA PARA ENCONTRA EL DIA
    
     if ( A <= 1582 )
          {
           printf ("el ano ingresado no pertenece al calendario gregoriano");
          }
     else
          {
                  if ((M>14)||(M<3))
                     {
                        printf ("error en el mes\n");
                     }
                  else
                      {
                               if ((Q<1)||(Q>31))
                                  {
                                  printf ("error en el dia del mes \n");
                                  }
                               else
                                   {
                                         if (A>1582)
                                             switch (H)
                                                     {
                                                      case 0 :
                                                        printf ("\n aquel dia era un Sabado\n");
                                                        break;
                                                       
                                                      case 1 :                                                     
                                                        printf ("\n aquel dia era un Domingo\n");
                                                        break;
                                                       
                                                      case 2 :
                                                        printf ("\n aquel dia era un Lunes\n");
                                                        break;
                                                       
                                                      case 3 :
                                                        printf ("\n aquel dia era un Martes\n");
                                                        break;
                                                       
                                                       case 4 :
                                                        printf ("\n aquel dia era un Miercoles\n");
                                                        break;
                                                       
                                                       case 5 :
                                                        printf ("\n aquel dia era un Jueves\n");
                                                        break;
                                                       
                                                       case 6 :
                                                        printf ("\n aquel dia era un Viernes\n");
                                                        break;

                                                        default:            
                                                        printf ("\n error de dia\n");
                                                     }
                                   }
                      }
          }
      system ("pause");
}