Unique k Characters

You are given a string s and an integer k. Your task is to construct a new string by taking the first occurrence of each distinct character from s (in the order they appear) until you have collected k characters, or you have reached the end of s.

If the number of unique characters in s is less than k, then output all unique characters. Formally, if we denote by \(U\) the ordered set of unique characters extracted from s, then the answer is the string formed by the first \(\min(|U|, k)\) characters.

For example, for s = "banana" and k = 3, the first unique characters are 'b', 'a', 'n', so the answer is "ban".

inputFormat

The input consists of two lines:

• The first line contains the string s.
• The second line contains the integer k.

outputFormat

Output a single line containing the resulting string after extracting at most k unique characters from s in their original order.

banana
3

ban