I'm trying to install elasticsearch following the instructions on this page:

I downloaded elasticsearch-6.3.1. Added lib directory to my system path:C:\ElasticSearch\elasticsearch-6.3.1\lib

But when I run the bin\elasticsearch.bat, I get following error:
"Error: Could not find or load main class C:\ElasticSearch\elasticsearch-6.3.1\lib\elasticsearch-cli-6.3.1.jar"

The elasticsearch-cli-6.3.1.jar is in the lib directory. I have java 8 installed.
C:\ElasticSearch\elasticsearch-6.3.1>java -version
java version "1.8.0_171"
Java(TM) SE Runtime Environment (build 1.8.0_171-b11)
Java HotSpot(TM) 64-Bit Server VM (build 25.171-b11, mixed mode)
I've been struggling with this error for few days now. Pleas let me know how I can get pass this so that I can start learning ElasticSearch.