Cannot understand why 2** is being used

Hey can somebody please explain why 2**a is being used in the solution to this problem?

Problem Link -> https://www.codechef.com/problems/ICL1906

Solution Link -> https://www.codechef.com/viewsolution/23700368

can’t find in the solution where 2** is used.

In python 2**x refers to 2^x.
it is used to raise power