Improve Project Euler problem 078 solution 1 (#5708)

* Add solution doctests

* Improve solution function

project_euler/problem_078/sol1.py

@@ -21,6 +21,12 @@ import itertools
 
 def solution(number: int = 1000000) -> int:
     """
+    >>> solution(1)
+    1
+
+    >>> solution(9)
+    14
+
     >>> solution()
     55374
     """
@@ -34,6 +40,7 @@ def solution(number: int = 1000000) -> int:
             if index > i:
                 break
             item += partitions[i - index] * sign
+            item %= number
             index += j
             if index > i:
                 break