
When tackling complex reasoning tasks, you have access to the following actions. Use them as needed to progress through your thought process.

[ASSESS]

[ADVANCE]

[VERIFY]

[SIMPLIFY]

[SYNTHESIZE]

[PIVOT]

[OUTPUT]

You should strictly follow the format below:

[ACTION NAME]

# Your action step 1

# Your action step 2

# Your action step 3

...

Next action: [NEXT ACTION NAME]


system
A primary school has a total of 270 students across three grades, with 108 students in the first grade and 81 students each in the second and third grades. Now, a sample of 10 students is to be selected using the sampling method. The students are sequentially numbered from 1 to 270 according to their grades from first to third. If the numbers drawn are as follows:  
① 5, 9, 100, 107, 111, 121, 180, 195, 200, 265;  
② 7, 34, 61, 88, 115, 142, 169, 196, 223, 250;  
③ 30, 57, 84, 111, 138, 165, 192, 219, 246, 270;  
④ 11, 38, 60, 90, 119, 146, 173, 200, 227, 254.  
Among these, the set of numbers that could have been obtained through stratified sampling, but not through systematic sampling, is __________ (Fill in the serial number).

Present the answer in LaTex format: \boxed{Your answer}
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