[RajatPawar]

pawn Код:

enum info
{
     pRace
}
new PlayerInfo[MAX_PLAYERS][info];
CMD:joinrace(playerid)
{
  //Your IsPlayerInHisOwnVehicle
  //Other conditions
  new temp=0;
  for(new i;i<MAX_PLAYERS;i++)
  {
   if(PlayerInfo[i][pRace]==1 
   if(temp==6) temp = -1;
   else temp++;
   
   }
   switch(temp)
   {
    case 1..5: 
    {//Teleport him to race and watever 
    PlayerInfo[playerid][pRace]=1;
    }
     case -1: //Sorry, race's full.
    }
    return 1;
}

Something like this, if you use an enum!