Using f(1)=1f(1)=1f(1)=1, f(2)=1f(2)=1f(2)=1, and f(n)=f(n−1)+f(n−2)f(n)=f(n-1)+f(n-2)f(n)=f(n−1)+f(n−2), what is f(6)f(6)f(6)?
888
131313
555
212121