int count_unknown_squares(const int board[MAX_SIZE][MAX_SIZE], int size) {
    // write your code here
    int count = 0;
    for (int i = 0; i < size; i++){
        for (int j = 0; j < size; j++){
            if (board[i][j] == UNKNOWN){
                count ++;
            }
        }
    }
    // replace this return statement
    return count;
}