Update sol1.py (#643)

small off by one error. Boundary condition: if len(number) =13 , we would need to check exactly 1 combination, namely number itself. However  for i in range(len(number)-13): will iterate 0 times.

project_euler/problem_08/sol1.py

@@ -2,7 +2,7 @@ import sys
 def main():
     LargestProduct = -sys.maxsize-1
     number=input().strip()
-    for i in range(len(number)-13):
+    for i in range(len(number)-12):
         product=1
         for j in range(13):
             product *= int(number[i+j])