diff --git a/practice/ocr-numbers/ocr_numbers.py b/practice/ocr-numbers/ocr_numbers.py
index 5e20881..f05a28a 100644
--- a/practice/ocr-numbers/ocr_numbers.py
+++ b/practice/ocr-numbers/ocr_numbers.py
@@ -1,3 +1,70 @@
+def process_section(section, digits):
+    """
+    Process a section of the input grid and convert it to a string of digits.
+
+    Args:
+        section (list): A list of strings representing a section of the input grid.
+        digits (dict): A dictionary mapping grid patterns to digits.
+
+    Returns:
+        str: A string of digits representing the section.
+
+    Examples:
+        >>> process_section([" _ ", "| |", "|_|", "   "], digits)
+        '0'
+    """
+    # Create chunks by joining every three characters in each row of the section
+    chunks = [''.join(row[i:i+3] for row in section) for i in range(0, len(section[0]), 3)]
+    
+    # Convert each chunk to a digit (or '?' if the chunk is not recognized)
+    output = [digits.get(chunk, '?') for chunk in chunks]
+    
+    # Join the digits into a string and return it
+    return ''.join(output)
+
+
 def convert(input_grid):
-    pass
+    """
+    Convert an OCR number grid to a string of digits.
+
+    Args:
+        input_grid (list): A list of strings representing the OCR number grid.
+
+    Returns:
+        str: A string of digits representing the OCR number grid.
+
+    Raises:
+        ValueError: If the number of input lines is not a multiple of four or
+                    if the number of input columns is not a multiple of three.
+
+    Examples:
+        >>> convert([" _ ", "| |", "|_|", "   ", "    ", "  |", "  |", "   "])
+        '0,1'
+    """
+    # Define the mapping from grid patterns to digits
+    digits = {
+        " _ | ||_|   ": "0",
+        "     |  |   ": "1",
+        " _  _||_    ": "2",
+        " _  _| _|   ": "3",
+        "   |_|  |   ": "4",
+        " _ |_  _|   ": "5",
+        " _ |_ |_|   ": "6",
+        " _   |  |   ": "7",
+        " _ |_||_|   ": "8",
+        " _ |_| _|   ": "9",
+    }
+
+    # Check if the number of input lines is a multiple of four
+    if len(input_grid) % 4 != 0:
+        raise ValueError("Number of input lines is not a multiple of four")
+    
+    # Check if the number of input columns is a multiple of three
+    if any(len(row) % 3 != 0 for row in input_grid):
+        raise ValueError("Number of input columns is not a multiple of three")
 
+    # Split the input grid into sections
+    sections = [input_grid[i:i+4] for i in range(0, len(input_grid), 4)]
+    
+    # Process each section and join the results with commas
+    return ','.join(process_section(section, digits) for section in sections)
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