class Index implements Operator
    {
        @Override
        public void execute(ExecutionContext context)
        {<FILL_FUNCTION_BODY>}

    }

            Stack<Object> stack = context.getStack();
            int n = ((Number)stack.pop()).intValue();
            if (n < 0)
            {
                throw new IllegalArgumentException("rangecheck: " + n);
            }
            int size = stack.size();
            stack.push(stack.get(size - n - 1));
        
<no_super_class>