Update langchain_example.py

Print results of the first call.

langchain_example.py

@@ -143,5 +143,6 @@ agent_chain = AgentExecutor.from_agent_and_tools(agent=agent, tools=tools, verbo
 call = agent_chain.run(
     "I have a cake that is about 3 centimenters high and 200 centimeters in radius. How much cake do I have?"
 )
+print(exec(call))
 call = agent_chain.run("What is 1+10?")
 print(exec(call))