Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
### Context:
CREATE TABLE table_28138035_20 (mens_singles VARCHAR, mens_doubles VARCHAR)
### Question:
How many players are there for mens singles when chen qi ma lin played mens doubles?
### Answer:
SELECT COUNT(mens_singles) FROM table_28138035_20 WHERE mens_doubles = "Chen Qi Ma Lin"