604B - More Cowbell - CodeForces Solution

#include<bits/stdc++.h>
using namespace std;
const int maxn=100010;
int n,m;
int a[maxn];
int main()
{
	scanf("%d%d",&n,&m);
	for(int i=1;i<=n;++i)
		scanf("%d",&a[i]);
	int single=min(n,m*2-n);
	int pair=n-single;
	int ans=a[n];
	for(int h=1,t=pair;h<t;++h,--t)
		ans=max(ans,a[h]+a[t]);
	printf("%d\n",ans);
	return 0;
}