How to get all elements from pandas dataframe and their corresponding values from a column?

Question

The dataframe looks like this (979 rows × 130 columns)

Col1	Col2	...	Col130	Value
1	4	...	7	A
2	5	...	8	B
3	6	....	9	C
...	...	....	...	...
979	222	....	10	D

How can I transform it to this in pandas?

Col1	Value
1	A
2	B
3	C
...	...
979	D
4	A
5	B
6	C
...	...
222	D
7	A
8	B
9	C
10	D
...	...