题目描述
Given are strings $s$ and $t$ of length $N$ each, both consisting of lowercase English letters.
Let us form a new string by alternating the characters of $S$ and the characters of $T$, as follows: the first character of $S$, the first character of $T$, the second character of $S$, the second character of $T$, $...$, the $N$\-th character of $S$, the $N$\-th character of $T$. Print this new string.