Login function

User login()
{
    ifstream flogin("users.dat",ios::binary);
    if(!flogin)
    {
         cout<<"No accounts have been created. Please restart and create an account first.";
         getch();
         exit(1);
    }
    else
    {
        char uname[15],pword[15];
        User u;
        int flag;
        int counter=0;
        a:
        system("cls");
        if(counter!=0)
        {
            flogin.open("users.dat",ios::binary);
        }
        flogin.seekg(0,ios::beg);
        cout<<"Username: ";
        fflush(stdin);
        gets(uname);
          while(flogin.read((char*)&u,sizeof(u)))
        {
            if(strcmp(uname,u.username)==0)
            {
                b:
                flag=0;
                system("cls");
                cout<<"Password: ";
                fflush(stdin);
                gets(pword);
                if(strcmp(pword,u.password)==0)
                {
                    break;
                }
                else
                {
                    cout<<"Wrong password. Please try again.";
                    getch();
                    goto b;
                }
            }
            else
            {
                flag=1;
            }
        }

        if(flag==1)
        {
           cout<<"Username does not exist. Try again.("<<(3-counter)<<" tries left)";
           getch();
           flogin.close();
           counter++;
           if(counter>=4)
           {
               exit(1);
           }
           else
           {
              goto a;
           }
        }
        else if(flag==0)
        {
           flogin.close();
           getch();
           return u;
        }
    }
}