I have two Lists and i wish to create a third

The first list is composed of 50 elements. This elements are integers varying from 1 to 7

The second list is composed of 7 elements.

The third list is composed of the same amount of elements of the first list but it follows the following pattern:

If index 0 of list 1 is equal to 1 than index 0 of list 3 is equal to index 0 of list 2.

If index 0 of list 1 is equal to 2 than index 0 of list 3 is equal to index 1 of list 2.

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If index 0 of list 1 is equal to 7 than index 0 of list 3 is equal to index 6 of list 2.

This criteria would be applied for all elements in list 1.

Thank you all in advance