Codeforces Round #334 (Div. 2) B. More Cowbell

题目连接

B. More Cowbell

time limit per test

2 seconds

memory limit per test

256 megabytes

input

standard input

output

standard output

Kevin Sun wants to move his precious collection of n cowbells from Naperthrill to Exeter, where there is actually grass instead of corn. Before moving, he must pack his cowbells into k boxes of a fixed size. In order to keep his collection safe during transportation, he won't place more than two cowbells into a single box. Since Kevin wishes to minimize expenses, he is curious about the smallest size box he can use to pack his entire collection.

Kevin is a meticulous cowbell collector and knows that the size of his i-th (1 ≤ i ≤ n) cowbell is an integer si. In fact, he keeps his cowbells sorted by size, so si - 1 ≤ si for any i > 1. Also an expert packer, Kevin can fit one or two cowbells into a box of size s if and only if the sum of their sizes does not exceed s. Given this information, help Kevin determine the smallest s for which it is possible to put all of his cowbells into k boxes of size s.

Input

The first line of the input contains two space-separated integers n and k (1 ≤ n ≤ 2·k ≤ 100 000), denoting the number of cowbells and the number of boxes, respectively.

The next line contains n space-separated integers s1, s2, ..., sn (1 ≤ s1 ≤ s2 ≤ ... ≤ sn ≤ 1 000 000), the sizes of Kevin's cowbells. It is guaranteed that the sizes si are given in non-decreasing order.

Output

Print a single integer, the smallest s for which it is possible for Kevin to put all of his cowbells into k boxes of size s.

Sample test(s)

input

2 12 5

output

7

input

4 32 3 5 9

output

9

input

3 23 5 7

output

8

Note

In the first sample, Kevin must pack his two cowbells into the same box.

In the second sample, Kevin can pack together the following sets of cowbells: {2, 3}, {5} and {9}.

In the third sample, the optimal solution is {3, 5} and {7}.

思路：当n<=k的时候当然是每个箱子装一个，当k<n<=2k时，先把按从大到小排序的前2n-k个单独放一个箱子，然后剩下的由最小的和最大的组合，第二小的和第二大的组合，以此类推。求出装得最多的箱子的大小

#include <stdio.h>#include <string.h>#define maxn 100000int c[maxn+5];int max(int a, int b) {return a>b?a:b;}int main(){    int n, k, res, i;    scanf("%d %d", &n, &k);    res = 0;    for(i = 0;i < n;i++) scanf("%d", &c[i]);    for(i = 0;i < n;i++)        res = max(res, c[i]);    for(i = 0;i < n - k;i++)            res = max(res, c[i] + c[2*(n - k)-1-i]);    printf("%d\n", res);}