import pandas as pd

sales = pd.DataFrame(
    {
        "region": ["East", "East", "East", "West", "West", "West", "North", "North"],
        "quarter": ["Q1", "Q1", "Q2", "Q1", "Q2", "Q2", "Q1", "Q3"],
        "revenue": [1200, 800, 950, 1400, 1100, 650, 500, 700],
    }
)