diff --git a/digital_image_processing/resize/resize.py b/digital_image_processing/resize/resize.py
index b7d493e70b4b..4fd222ccd6c6 100644
--- a/digital_image_processing/resize/resize.py
+++ b/digital_image_processing/resize/resize.py
@@ -11,7 +11,7 @@ class NearestNeighbour:
 
     def __init__(self, img, dst_width: int, dst_height: int):
         if dst_width < 0 or dst_height < 0:
-            raise ValueError(f"Destination width/height should be > 0")
+            raise ValueError("Destination width/height should be > 0")
 
         self.img = img
         self.src_w = img.shape[1]
diff --git a/maths/number_of_digits.py b/maths/number_of_digits.py
new file mode 100644
index 000000000000..12717065149e
--- /dev/null
+++ b/maths/number_of_digits.py
@@ -0,0 +1,18 @@
+def num_digits(n: int) -> int:
+    """
+    Find the number of digits in a number.
+
+    >>> num_digits(12345)
+    5
+    >>> num_digits(123)
+    3
+    """
+    digits = 0
+    while n > 0:
+        n = n // 10
+        digits += 1
+    return digits
+
+
+if __name__ == "__main__":
+    print(num_digits(12345))   # ===> 5