Igra

Mirko and Slavko are bored on their skiing trip, so they invented a game. First Mirko picks a number $N$. Slavko then writes down the $N$ letters he will use to build his word. After that Mirko writes a word of $N$ letters. Slavko has to build a word that uses every letter he chose, with no letter left over, so that no position of his word holds the same letter as the same position of Mirko's word. To make the game tighter, Slavko must find the lexicographically smallest such word. Such a word always exists. The two are still young and know only the three letters a, b and c, which greatly affects their programming skills.

The first line contains a positive integer $N$ ($1 \le N \le 5000$).
The second line contains the letters Slavko chose, a string of length $N$ made of the lowercase letters a, b and c.
The third line contains the word Mirko wrote, a string of length $N$ made of the lowercase letters a, b and c.
Every input admits at least one word that satisfies the condition.

In test cases worth 40 points in total, $1 \le N \le 20$.

Print the word Slavko found on the first line.