mk_qwerty

SELECT
	book.NAME, 
	SUM(IF(store.CITY = 'Moscow', QUANTITY, 0)) AS CITY1_QUANTITY,
	SUM(IF(store.CITY = 'London', QUANTITY, 0)) AS CITY2_QUANTITY,
	SUM(IF(store.CITY = 'Moscow', QUANTITY, 0)- IF(store.CITY = 'London', QUANTITY, 0)) AS DIFF_QUANTITY
FROM book
LEFT JOIN book_store ON book_store.BOOK_ID = book.ID
JOIN store ON store.ID = book_store.STORE_ID
WHERE store.CITY IN ('Moscow', 'London')
GROUP BY book.NAME;

не могу найти ошибку

int y = n/2;
... 
&& (y > (n-1))

int deadEnds = 0;
... 
100*deadEnds/trials == 0