
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
The store sells 20 items, each priced uniquely in whole numbers from 1 to 20 rubles. The store has a promotion: when purchasing any 5 items, one of them is given for free, and the customer can choose which one. Vlad wants to buy all 20 items in this store, paying as little as possible. How many rubles does he need? (Each of the 20 items is sold in a single unit.)

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