Problems
Fibonacci strings generation
Fibonacci strings generation
Generate $n$-th Fibonacci string that is defined with the next recurrent formula:
\begin{itemize}
\item $f(0) = "a"$;
\item $f(1) = "b"$;
\item $f(n) = f(n - 1) + f(n - 2)$, where $"+"$ operation means concatenation
\end{itemize}
For example, $f(3) = f(2) + f(1) = (f(1) + f(0)) + f(1) = "b" + "a" + "b" = "bab"$.
\InputFile
One integer $n~(0 \le n \le 20)$.
\OutputFile
Print the $n$-th Fibonacci string.
Input example #1
3
Output example #1
bab
Input example #2
5
Output example #2
babbabab