diff --git a/project_euler/problem_03/sol3.py b/project_euler/problem_03/sol3.py
new file mode 100644
index 000000000000..5fe45df59984
--- /dev/null
+++ b/project_euler/problem_03/sol3.py
@@ -0,0 +1,63 @@
+"""
+Problem:
+The prime factors of 13195 are 5,7,13 and 29. What is the largest prime factor
+of a given number N?
+
+e.g. for 10, largest prime factor = 5. For 17, largest prime factor = 17.
+"""
+
+
+def solution(n: int) -> int:
+    """Returns the largest prime factor of a given number n.
+
+    >>> solution(13195)
+    29
+    >>> solution(10)
+    5
+    >>> solution(17)
+    17
+    >>> solution(3.4)
+    3
+    >>> solution(0)
+    Traceback (most recent call last):
+        ...
+    ValueError: Parameter n must be greater or equal to one.
+    >>> solution(-17)
+    Traceback (most recent call last):
+        ...
+    ValueError: Parameter n must be greater or equal to one.
+    >>> solution([])
+    Traceback (most recent call last):
+        ...
+    TypeError: Parameter n must be int or passive of cast to int.
+    >>> solution("asd")
+    Traceback (most recent call last):
+        ...
+    TypeError: Parameter n must be int or passive of cast to int.
+    """
+    try:
+        n = int(n)
+    except (TypeError, ValueError):
+        raise TypeError("Parameter n must be int or passive of cast to int.")
+    if n <= 0:
+        raise ValueError("Parameter n must be greater or equal to one.")
+    i = 2
+    ans = 0
+    if n == 2:
+        return 2
+    while n > 2:
+        while n % i != 0:
+            i += 1
+        ans = i
+        while n % i == 0:
+            n = n / i
+        i += 1
+
+    return int(ans)
+
+
+if __name__ == "__main__":
+    # print(solution(int(input().strip())))
+    import doctest
+
+    doctest.testmod()
diff --git a/project_euler/problem_08/sol3.py b/project_euler/problem_08/sol3.py
new file mode 100644
index 000000000000..fe9901742201
--- /dev/null
+++ b/project_euler/problem_08/sol3.py
@@ -0,0 +1,83 @@
+# -*- coding: utf-8 -*-
+"""
+The four adjacent digits in the 1000-digit number that have the greatest
+product are 9 × 9 × 8 × 9 = 5832.
+
+73167176531330624919225119674426574742355349194934
+96983520312774506326239578318016984801869478851843
+85861560789112949495459501737958331952853208805511
+12540698747158523863050715693290963295227443043557
+66896648950445244523161731856403098711121722383113
+62229893423380308135336276614282806444486645238749
+30358907296290491560440772390713810515859307960866
+70172427121883998797908792274921901699720888093776
+65727333001053367881220235421809751254540594752243
+52584907711670556013604839586446706324415722155397
+53697817977846174064955149290862569321978468622482
+83972241375657056057490261407972968652414535100474
+82166370484403199890008895243450658541227588666881
+16427171479924442928230863465674813919123162824586
+17866458359124566529476545682848912883142607690042
+24219022671055626321111109370544217506941658960408
+07198403850962455444362981230987879927244284909188
+84580156166097919133875499200524063689912560717606
+05886116467109405077541002256983155200055935729725
+71636269561882670428252483600823257530420752963450
+
+Find the thirteen adjacent digits in the 1000-digit number that have the
+greatest product. What is the value of this product?
+"""
+import sys
+
+N = """73167176531330624919225119674426574742355349194934\
+96983520312774506326239578318016984801869478851843\
+85861560789112949495459501737958331952853208805511\
+12540698747158523863050715693290963295227443043557\
+66896648950445244523161731856403098711121722383113\
+62229893423380308135336276614282806444486645238749\
+30358907296290491560440772390713810515859307960866\
+70172427121883998797908792274921901699720888093776\
+65727333001053367881220235421809751254540594752243\
+52584907711670556013604839586446706324415722155397\
+53697817977846174064955149290862569321978468622482\
+83972241375657056057490261407972968652414535100474\
+82166370484403199890008895243450658541227588666881\
+16427171479924442928230863465674813919123162824586\
+17866458359124566529476545682848912883142607690042\
+24219022671055626321111109370544217506941658960408\
+07198403850962455444362981230987879927244284909188\
+84580156166097919133875499200524063689912560717606\
+05886116467109405077541002256983155200055935729725\
+71636269561882670428252483600823257530420752963450"""
+
+
+def streval(s: str) -> int:
+    ret = 1
+    for it in s:
+        ret *= int(it)
+    return ret
+
+
+def solution(n: str) -> int:
+    """Find the thirteen adjacent digits in the 1000-digit number n that have
+    the greatest product and returns it.
+ 
+    >>> solution(N)
+    23514624000
+    """
+    LargestProduct = -sys.maxsize - 1
+    substr = n[:13]
+    cur_index = 13
+    while cur_index < len(n) - 13:
+        if int(n[cur_index]) >= int(substr[0]):
+            substr = substr[1:] + n[cur_index]
+            cur_index += 1
+        else:
+            LargestProduct = max(LargestProduct, streval(substr))
+            substr = n[cur_index : cur_index + 13]
+            cur_index += 13
+    return LargestProduct
+
+
+if __name__ == "__main__":
+    print(solution(N))