TheAlgorithms · cclauss · Sep 25, 2020 · Sep 25, 2020 · Sep 25, 2020 · Sep 25, 2020
diff --git a/project_euler/problem_97/__init__.py b/project_euler/problem_97/__init__.py
@@ -0,0 +1 @@
+#
diff --git a/project_euler/problem_97/sol1.py b/project_euler/problem_97/sol1.py
@@ -0,0 +1,46 @@
+"""
+The first known prime found to exceed one million digits was discovered in 1999,
+and is a Mersenne prime of the form 2**6972593 − 1; it contains exactly 2,098,960
+digits. Subsequently other Mersenne primes, of the form 2**p − 1, have been found
+which contain more digits.
+However, in 2004 there was found a massive non-Mersenne prime which contains
+2,357,207 digits: (28433 * (2 ** 7830457 + 1)).
+
+Find the last ten digits of this prime number.
+"""
+
+
+def solution(n: int = 10) -> str:
+    """
+    Returns the last n digits of NUMBER.
+    >>> solution()
+    '8739992577'
+    >>> solution(8)
+    '39992577'
+    >>> solution(1)
+    '7'
+    >>> solution(-1)
+    Traceback (most recent call last):
+        ...
+    ValueError: Invalid input
+    >>> solution(8.3)
+    Traceback (most recent call last):
+        ...
+    ValueError: Invalid input
+    >>> solution("a")
+    Traceback (most recent call last):
+        ...
+    ValueError: Invalid input
+    """
+    if not isinstance(n, int) or n < 0:
+        raise ValueError("Invalid input")
+    MODULUS = 10 ** n
+    NUMBER = 28433 * (pow(2, 7830457, MODULUS)) + 1
+    return str(NUMBER % MODULUS)
+
+
+if __name__ == "__main__":
+    from doctest import testmod
+
+    testmod()
+    print(f"{solution(10) = }")