Problem Description

There are $ N $ members in the club called Paken. Each member is numbered from $ 1 $ to $ N $ in order of their age.
The competitive programming skill of member $ i $ is $ A_i $.
In competitive programming, team battles are common. Paken defines the "team combat power" as the value of the lowest skill level in the team.
For example, the combat power of a team with members having skills $ 5 $, $ 4 $, and $ 10 $ is $ 4 $.

Suddenly, competitive programming was added as an event in the 2020 Tokyo Olympics, which requires teams of exactly $ D $ members.
All members of Paken want to apply for the selection. Therefore, Paken decided to divide the teams as follows:

• Allow as many people as possible to apply for the selection.
• Maximize the total team combat power.
• No person can be in multiple teams.

What will be the total team combat power?

Input Format

The input is given from the standard input in the following format:

$ N $ $ D $ $ A_1 $ $ A_2 $ $ A_3 $ ... $ A_N $

Output Format

Output the total team combat power as an integer on one line according to the method described in the problem.

Sample Input and Output

Sample Input #1

4 2
20 18 12 24

Sample Output #1

32

Sample Input #2

5 5
8 6 9 1 20

Sample Output #2

1

Sample Input #3

6 8
1268 1755 2315 1071 1229 1101

Sample Output #3

0

Sample Input #4

8 3
1345 1355 1390 1285 1171 936 1272 855

Sample Output #4

2516

Notes/Hints

Constraints

• $ N $ is an integer between $ 1 $ and $1\ 000$ inclusive.
• $ D $ is an integer between $ 1 $ and $ 10 $ inclusive.
• $ A_i $ is an integer between $ 1 $ and $4\ 208$ inclusive.
• There are no members with the same skill level.

Subtasks

Subtask $ 1 $ \[$ 25 $ points\]

• Satisfies $ N = D $.

Subtask $ 3 $ \[$ 75 $ points\]

• No additional constraints.

Sample Explanation 1

The skills of the members are $ {20, 18, 12, 24} $ from member $ 1 $ onwards. If the teams are decided as follows, the total combat power is $ 20 + 12 = 32 $.
- Team consisting of members $ 1 $ and $ 4 $: Combat power is $ min(20, 24) = 20 $.
- Team consisting of members $ 2 $ and $ 3 $: Combat power is $ min(18, 12) = 12 $.

Sample Explanation 2

Since $ N = D $, only one team can be formed, and all members can participate in the selection without any excess or shortage. Therefore, the total combat power is $ min(8, 6, 9, 1, 20) = 1 $.

Sample Explanation 3

Since $ N < D $, no teams can be formed. Therefore, the total combat power is $ 0 $.

Sample Explanation 4

Since $ 8 $ members are to be divided into $ 3 $ member teams, $ 2 $ members will inevitably be left out.

见题面 Input 部分

见题面 Output 部分