
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 customer enters a store, selects an item costing 20 rubles, and gives the seller a 100-ruble banknote. The seller notices that he doesn't have any change. He goes to a neighboring department, exchanges the 100 rubles, and gives the customer the item and the change. The customer leaves. Suddenly, the seller from the neighboring department returns with the 100-ruble note, claiming it is fake. The first seller then gives him a real 100-ruble note of his own. How much did the first seller lose in total?

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