Update 'README.md'

README.md

@@ -68,6 +68,7 @@ ___
 - [Ladner's Theorem](https://en.wikipedia.org/wiki/NP-intermediate)
 - [Levin Algorithm](https://en.wikipedia.org/wiki/P_versus_NP_problem#Polynomial-time_algorithms)
 - [Nim](https://en.wikipedia.org/wiki/Nim)
+- [Log Sum Inequality](https://en.wikipedia.org/wiki/Log_sum_inequality)