'''
Problem Statement:
If we list all the natural numbers below 10 that are multiples of 3 or 5,
we get 3,5,6 and 9. The sum of these multiples is 23.
Find the sum of all the multiples of 3 or 5 below N.
'''
from __future__ import print_function
try:
    raw_input          # Python 2
except NameError:
    raw_input = input  # Python 3
n = int(raw_input().strip())
sum = 0
terms = (n-1)/3
sum+= ((terms)*(6+(terms-1)*3))/2 #sum of an A.P.
terms = (n-1)/5
sum+= ((terms)*(10+(terms-1)*5))/2
terms = (n-1)/15
sum-= ((terms)*(30+(terms-1)*15))/2
print(sum)

Project Euler/Problem 01/sol2.py
'''
Problem Statement:
If we list all the natural numbers below 10 that are multiples of 3 or 5,
we get 3,5,6 and 9. The sum of these multiples is 23.
Find the sum of all the multiples of 3 or 5 below N.
'''
from __future__ import print_function
try:
    raw_input          # Python 2
except NameError:
    raw_input = input  # Python 3
n = int(raw_input().strip())
sum = 0
terms = (n-1)//3
sum+= ((terms)*(6+(terms-1)*3))//2 #sum of an A.P.
terms = (n-1)//5
sum+= ((terms)*(10+(terms-1)*5))//2
terms = (n-1)//15
sum-= ((terms)*(30+(terms-1)*15))//2
print(sum)

Project Euler/Problem 01/sol2.py
diff --git a/Project Euler/Problem 01/sol2.py b/Project Euler/Problem 01/sol2.py
index d330387e98ab..2b7760e0bfff 100644
--- a/Project Euler/Problem 01/sol2.py	
+++ b/Project Euler/Problem 01/sol2.py	
@@ -11,10 +11,10 @@
     raw_input = input  # Python 3
 n = int(raw_input().strip())
 sum = 0
-terms = (n-1)/3
-sum+= ((terms)*(6+(terms-1)*3))/2 #sum of an A.P.
-terms = (n-1)/5
-sum+= ((terms)*(10+(terms-1)*5))/2
-terms = (n-1)/15
-sum-= ((terms)*(30+(terms-1)*15))/2
+terms = (n-1)//3
+sum+= ((terms)*(6+(terms-1)*3))//2 #sum of an A.P.
+terms = (n-1)//5
+sum+= ((terms)*(10+(terms-1)*5))//2
+terms = (n-1)//15
+sum-= ((terms)*(30+(terms-1)*15))//2
 print(sum)

ProjectEuler -- Problem 1 -- solv2.py -- Error
For the Input ```1000``` I get ```233366.4```. The correct answer should be ```233168``` 
See [file](https://github.com/TheAlgorithms/Python/blob/master/Project%20Euler/Problem%2001/sol2.py)
