def drop_duplicates(df):
    """Drop duplicate rows and reindex.
    
    Args:
        df (pd.DataFrame): Dataframe.
    
    Returns:
        pd.DataFrame: Dataframe with the replaced value.
    
    Examples:
        >>> df = pd.DataFrame({'letters':['b','b','c'], 'numbers':[2,2,3]})
        >>> drop_duplicates(df)
          letters  numbers
        0       b        2
        1       c        3
    """
    return df.drop_duplicates().reset_index(drop=True)