n = 13          --> push 1 (= 13%2)
n = 6  (= 13/2) --> push 0 (= 6%2)
n = 3  (=  6/2) --> push 1 (= 3%2)
n = 1  (=  3/2) --> push 1 (= 1%2)
n = 0  (=  1/2)

pop --> 1
pop --> 1
pop --> 0
pop --> 1

Output: 1101