K Smallest Substring

In a string consisting only of 0/1, choose a substring that contains exactly k ones; first minimize the length, and among equal lengths take the lexicographically smallest. The statement guarantees that an answer exists.

输入格式

The first line contains the binary string s; the second line contains the integer k. This site follows the original length range 1≤k≤|s|≤1000, and explicitly adds the statement's guarantee that 1≤k≤(the total number of 1s in s).

输出格式

Output the valid substring that is smallest by (length, lexicographic order).

样例 1

输入：

0101101
3

输出：

1011

样例 2

输入：

111
1

输出：

1

样例 3

输入：

0010100
1

输出：

1