## Iceberg Hopping

Some penguins are going iceberg-hopping!

There are initially \(N\) floating icebergs, each staying afloat for another \(t_i\) seconds. After \(t_i\) seconds the \(i\)-th iceberg will sink and become unusable.

Bob the penguin can jump across a maximum of \(K\) icebergs at once (see the sample explanation for more information) and always starts on the first iceberg.

What is the latest time Bob can start his iceberg-hopping in order to reach the \(N\)-th iceberg? Bob is a very fast penguin, we will assume that no time will be wasted when he's iceberg-hopping.

#### Input Specification

The first line of the input will contain two integers \(N\) and \(K\) \((1 \le N, K \le 10^5)\), indicating the number of icebergs and the number of icebergs he can jump over.

The next line of the input will each contain an integer \(t_i\) ranging from \(0\) to \(10^9\) inclusive, indicating the number of seconds remaining before the \(i\)-th iceberg becomes unusable.

#### Output Specification

Output an integer, representing the latest time (in seconds) Bob can start his iceberg-hopping run.

#### Sample Input 1

```
5 2
2 1 0 1 3
```

#### Sample Output 1

`1`

#### Sample Explanation 1

When \(t = 0\), all icebergs are still floating. Bob can reach the iceberg \(5\) in multiple ways.

When \(t = 1\), there is only **one** way to reach the last iceberg. Bob must jump from iceberg \(1\) to iceberg \(2\), iceberg \(2\) to iceberg \(4\), and finally from iceberg \(4\) to iceberg \(5\).

When \(t = 2\), iceberg \(2\) and \(4\) both sink, leving no possible way for Bob to reach the end. This indicates that \(t = 1\) is the last possible time Bob can start.

#### Sample Input 2

```
1 1
0
```

#### Sample Output 2

`0`

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