In this task, you are given a country name, and you need to return the year in which the country became independent. Independence is a nation's independence or statehood, usually after ceasing to be a group or part of another nation or state, or more rarely after the end of military occupation.
One example: Angola
Solution is here: 1975
Explanation: 1975 is the year of independence of Angola.

Now, solve this: Sierra Leone
Solution:
1961