Update Extra

Author: Ashishgup1

Extra

@@ -90,5 +90,6 @@
 //Problem 2 (Number of ways to place elements such that adjacent are different and given L and R) : https://www.codechef.com/BLUP2019/problems/AHAPH/
 //Problem 3 (Merge Sort Tree): https://codeforces.com/contest/369/problem/E
 //Problem 4 ([N/x] ranges): https://www.hackerrank.com/contests/hourrank-7/challenges/tile-painting-revisited/problem
+(https://www.hackerearth.com/practice/math/number-theory/basic-number-theory-2/practice-problems/algorithm/numbers-summation/)
 Resources:
 https://www.careerbless.com/aptitude/qa/permutations_combinations_imp7.php