Problem Statement

Let us define $\mathrm{mex}(x_1, x_2, x_3, \dots, x_k)$ as the smallest non-negative integer that does not occur in $x_1, x_2, x_3, \dots, x_k$.
You are given an integer sequence of length N: $A = (A_1, A_2, A_3, \dots, A_N)$.
For each integer i such that $0 \le i \le N - M$, we compute $\mathrm{mex}(A_{i + 1}, A_{i + 2}, A_{i + 3}, \dots, A_{i + M}).$ Find the minimum among the results of these N - M + 1 computations.

Input

Input is given from Standard Input in the following format:
N M
$A_1 A_2 A_3 \dots A_N$

Output

Print the answer.

Constraints

• $1 \le M \le N \le 1.5 \times 10^6$
• $0 \le A_i \lt N$
• All values in input are integers.

Sample Input 1

3 2
0 0 1

Sample Output 1

1

We have:

• for i = 0: $\mathrm{mex}(A_{i + 1}, A_{i + 2}) = \mathrm{mex}(0, 0) = 1$
• for i = 1: $\mathrm{mex}(A_{i + 1}, A_{i + 2}) = \mathrm{mex}(0, 1) = 2$

Thus, the answer is the minimum among 1 and 2, which is 1.

Sample Input 2

3 2
1 1 1

Sample Output 2

0

We have:

• for i = 0: $\mathrm{mex}(A_{i + 1}, A_{i + 2}) = \mathrm{mex}(1, 1) = 0$
• for i = 1: $\mathrm{mex}(A_{i + 1}, A_{i + 2}) = \mathrm{mex}(1, 1) = 0$

Sample Input 3

3 2
0 1 0

Sample Output 3

2

We have:

• for i = 0: $\mathrm{mex}(A_{i + 1}, A_{i + 2}) = \mathrm{mex}(0, 1) = 2$
• for i = 1: $\mathrm{mex}(A_{i + 1}, A_{i + 2}) = \mathrm{mex}(1, 0) = 2$

Sample Input 4

7 3
0 0 1 2 0 1 0

Sample Output 4

2

见题面 Input 部分

见题面 Output 部分