# Write a Pandas program to create a series of Timestamps from a DataFrame of integer or string columns. Also create a series of Timestamps using specified columns.  
 import pandas as pd
df = pd.DataFrame({'year': [2018, 2019, 2020],
                   'month': [2, 3, 4],
                   'day': [4, 5, 6],
                   'hour': [2, 3, 4]})
print("Original dataframe:")
print(df)
result = pd.to_datetime(df)
print("\nSeries of Timestamps from the said dataframe:")
print(result)
print("\nSeries of Timestamps using specified columns:")
print(pd.to_datetime(df[['year', 'month', 'day']]))
