here according to the question.
ans will be 7^n.
I have used the formula to carry out
7^n=7^(n/2)+7^(n/2) formula
I am getting correct ans on the test Cases But Wrong answer on Submission
HERE is the Link Of my Solution:-

calc function returns int but the answer can be greater than the int size.

function ‘cal’ should return long long int. You might check your code for n=101, it gives a negative answer.