inline int get_sum( int x, int y )
{
	int sum = 0;
	for( int i = x ; i != 0; i -= lowbit(i)) //这里原来写成了x
	    for( int j = y ; j != 0; j -= lowbit(j)) //这里原来写成了y
	        sum += tre[i][j];
	return sum;
}