Categorize the days of the week based on their starting alphabet.
Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday
S - Sunday, Saturday
M - Monday
W - Wednesday
T - Tuesday, Thursday
F - Friday
Below is an instruction that describes a task, paired with an input that provides further context. Write a response that appropriately completes the request.
### Instruction: Categorize the days of the week based on their starting alphabet.
Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday
### Input: 
### Response: S - Sunday, Saturday
M - Monday
W - Wednesday
T - Tuesday, Thursday
F - Friday