SPOJ ARITH2 using ScriptEngineManager gives TLE. Please help.

Problem: http://www.spoj.com/problems/ARITH2/

Solution 1: http://ideone.com/jdUYbd

I know the problem can be done using switch case very easily,but I learnt about ScriptEngineManager recently and want to apply it for this particular program. I don't want to use switch case. Is there any way to optimize my code such that it gets accepted?

Thank You