Problems with IF Statement and Arrays

//define the main constant 
#define MAX_PASSENGERS  10
//some to make the code more readable
#define  EMPTY                     0
#define  FULL                       1
#define  FIRST_CLASS          1
#define  ECONOMY               2
//array of seats
int         iSeats[MAX_PASSENGERS];

int main()
{
int response;

int    iPassengers=0,i;
//init array
for(i=0;i<MAX_PASSENGERS;i++)
     iSeats[i]=0;//all set to empty

//for each passengers until max
while(iPassengers<MAX_PASSENGERS)
{
     //a "do while" loop is used where the code MUST run at least once
    do
    {
         cout<<"Please type 1 for First Class\n";
          cout<<"Please type 2 for Economy Class. ";
         cin>>response;//no need to prime the loop as we get the input here BEFORE we test the loop exit condition
    }
    while (response != FIRST_CLASS && response !=ECONOMY)


    //now will have the TYPE of seat
    iPassenger++;//increase the passengers 



    //now need to find the first empty seat in the section the user has choosen
     if(response==FIRST_CLASS)//first class
     {
           / /look for an empty seat
             i=0;//init loop counter
            while(iSeats[i]==FULL  && i<MAX_PASSENGERS/2)//watch for arrays going out of the space you have allocated
                 i++;//more thru array looking fo an empty seat 

             //now have either run out of seats or have an empty one
             if(i>=MAX_PASSENGERS/2)//no empty seats, WHAT WILL YOU DO?
             else //got a seat.
             {
                     iSeat[i]=FULL;
                     //INFORM USER OF SEAT NUMBER
              }
      }
//ect

return 1;
}