How can I merge df1 and df2 into df3?

Question

I use pandas library

import pandas as pd

I have a data like this:

data = pd.DataFrame({ 'A':[1,2,3],
                      'B':[4,5,6],
                      'C':[7,8,9],
                      'D':[1,3,5],
                      'E':[5,3,6],
                      'F':[7,4,3] })

Take some special values

df1 = data.iloc[:, 0:2].values
df2 = data.iloc[:, 3:5].values

Values in df1

[[1 4]
 [2 5]
 [3 6]]

Values in df2

[[1 5]
 [3 3]
 [5 6]]

I want to have a df3 like this one:

[[1 4]
 [2 5]
 [3 6]
 [1 5]
 [3 3]
 [5 6]]