How to express position of item in GridView

public class MyActivity extends Activity {

    String[] choices = new String[12];

    {
        choices[0] = "A";
        choices[1] = "B";
        choices[2] = "C";
        choices[3] = "D";
        choices[4] = "E";
        choices[5] = "F";
        choices[6] = "G";
        choices[7] = "H";
        choices[8] = "I";
        choices[9] = "J";
        choices[10] = "K";
        choices[11] = "L";

    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_my);

        final GridView gridview = (GridView) findViewById(R.id.gridview);

        ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, choices);

        gridview.setAdapter(adapter);

        gridview.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            public void onItemClick(AdapterView<?> parent, View v,
                                    int position, long id) {

                v.setBackgroundColor(Color.WHITE);
                if (v.getTag(position).equals(5) && v.getTag(position).equals(6) && v.getTag(position).equals(5)) {
                    Toast.makeText(getApplicationContext(), "Line!", Toast.LENGTH_LONG).show();
                }


            };

        });


        }

    }