Get Substring

In a string containing only 0/1, find a substring with exactly k 1s; first minimize the length, and among equal lengths take the lexicographically smallest. The statement guarantees an answer exists.

输入格式

The first line is the binary string s; the second line is k. Source range: 1≤k≤|s|≤1000, and s contains at least k 1s.

输出格式

Output the chosen substring (without quotes).

样例 1

输入：

0101101
3

输出：

1011

样例 2

输入：

101
1

输出：

1

样例 3

输入：

1011
2

输出：

11