Unable to assign more than one digit in the CLI of arithmetic example

bin> ./client.sh assign --name a --value 11
/Users/snemuri/git/incubator-ratis/ratis-examples/src/main/bin/../../../target/ratis-examples-0.1.1-alpha-SNAPSHOT.jar
Exception in thread "main" java.lang.IllegalArgumentException: Invalid expression 11 Try something like: 'a+b' or '2'
	at org.apache.ratis.examples.arithmetic.cli.Assign.createExpression(Assign.java:73)
	at org.apache.ratis.examples.arithmetic.cli.Assign.operation(Assign.java:53)
	at org.apache.ratis.examples.arithmetic.cli.Client.run(Client.java:50)
	at org.apache.ratis.examples.arithmetic.Runner.main(Runner.java:62)