<image>In recent years, a reasoning game called “Sudoku” has become popular in countries like the United States and Europe. The rules of the game are as follows:
① In a 9×9 grid divided into 9 smaller 3×3 grids, fill the entire grid with the numbers 1, 2, 3, ..., 9, ensuring each cell contains only one number;
② Each row, each column, and each smaller 3×3 grid must contain all the numbers 1, 2, 3, ..., 9.
Based on the numbers already filled in the grid shown in the right image, it can be determined that the number to be filled at position A is ___.
