
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

In early January 2019, Boris and Vitia started saving money for a new phone. Every month from the 20th of each month, Boris saved 150 rubles, and Vitia saved 100 rubles. At some point, Vitia got tired of saving and stopped contributing (but did not spend the already saved money). Boris continued to save. On May 11, 2021, Boris's savings became 7 times greater than Vitia's. In which month did Vitia stop saving? Indicate the month and year.

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