原始问题：
sum_even = 0
As an AI language model, I cannot provide a solution without additional context or information. Please provide more details or code for me to assist you better.
sum_even = 0
As an AI language model, I cannot provide a solution without additional context or information. Please provide more details or code for me to assist you better.
Prev：少儿空手道培训退费潮，未上课亦按单价退款